ABSTRACTS and EXTRACTS of publications and reports
Response to a recent debate about radiation and radon in granite kitchen counter-tops
On May 8, 2008 radio station KHOU Channel 11 in Houston, Texas released a video that presented a one-sided account of radiation levels in granite and associated radon levels in homes that contain natural granite kitchentops. To support their account they engaged a particle physicist from Rice University to undertake radiation analyses of a number of kitchentops using a portable Na(I) gamma-ray spectrometer.
I have listened and watched the recent debate with some interest and absorbed the passionate, the informed and the uninformed responses that have been presented. In all these responses there was one very conspicuous void – that of a qualified geoscientist who has the scientific and technical background and who has been intimately involved in the stone industry for many years.
The issue of radiation in granite and the emission of radon from the granite kitchen countertops has been raised a number of times over the last 15 years and there seems little doubt that the issue this time was also prompted by the quartz surfaces and plastic industry who are continually attempting to undermine the qualities/virtues of natural stone by misinformation crusades. By publicly suggesting that kitchen countertops might be radioactive invariably elicits a degree of concern and panic among uninformed consumers. Consumers have neither the means to determine the radiation levels in their homes nor any avenue by which they can extract such information from the fabricators or wholesalers of stone. However, they can purchase relatively cheap radon meters and undertake a crude investigation of the radon gas levels in various parts of their homes.
…………A final note is necessary on the rather ludicrous notion that regular maintenance of granite kitchen countertops (including sealing the surface annually) will in some way influence the radiation flux and radon emissions from that surface.
As for the ill-conceived and impractical idea on the testing of every slab, tile and block of stone that enters into the US and is produced in the US clearly the Rice University particle physicist has little knowledge of the diverse stone industry. All slate would require testing, all sandstone products (because of the possibility of thin beds of natural heavy mineral concentrations), all sand used for construction, the gypsum used to make plaster for walls and ceilings, and every aggregate source that uses its product to make concrete. In almost all dwellings these other construction products far exceed the amount of granite that is used.
A commonly encountered and quite serious problem these days is the function of the testing laboratory and laboratory personnel not only in the testing but also in the interpretation of the data. Laboratories (and that includes many university departments where instrumental testing is carried out) employ technicians who are trained in most aspects of instrumentation and in the conduction of certain tests. They are generally not trained in the understanding of the materials they are testing nor in the interpretation or significance of the results.
Instrumentation specialists should limit themselves to the understanding of the instruments that they are using for testing and engage a suitably qualified scientist to assess and interpret the results, even when the testing appears to be straight-forward.
It is not a difficult task to determine whether a stone variety belongs to the huge “benign” group that does not require any further testing or belongs to the small group that is “sus” and requires further examination. It simply requires a macroscopic and binocular microscope examination of a polished tile together with a petrographic analysis of a thin-section of that stone (a sliver ground to exactly 30 microns thickness) by a stone specialist or stone scientist with a high level of expertise in petrography, petrology and building stone.
Some aspects of engineered stone that are not usually advertised
Engineered stone products have made a substantial impact on the natural stone industries in most countries. Clearly, they have taken a significant market share of all products used in domestic and commercial applications, be it stone, laminex, wood, or stainless steel. In Australia, marble and granite fabricators who were using about 5% of engineered product to 95% natural stone at the beginning of 2002 were abundantly aware that the drive of the market was causing a rapid shift in this ratio so that by the end of 2002 the ratio for some of these fabricators was in favour of the synthetic material. Stone fabricators who resisted the use of synthetic material were forced by competitive factors to adopt new strategies which incorporated the manufacture of this synthetic material. There are a number of reasons for this sudden surge of popularity including advertising and promotions, especially directed towards interior designers and developers. Much of this advertising compares the virtues of the synthetic product against natural stone. However, not all of the advertising is honest and it is the misrepresentations that are made verbally and in written form that has the natural stone industry objecting.
Among the many deficiencies of the synthetic products are the high coefficient of expansion (about 4x that of natural stone), fading with UV, generation of VOC’s (especially if in enclosed areas), easy chipping of edges, frequent fracturing and catastrophic failure of bench-tops, repair difficulties, difficulty in matching the surface with the edging, discolouration, bowing, delamination from the carcass, may catch fire with applied heat, dates the installation, and commonly poor after-sales support.
To seal or not to seal the Indian granite paving at Brisbane Square Project
The Brisbane Square Project is a new commercial/office complex in the Brisbane CBD. As part of the construction, honed, grey Sindoor Brown granite and exfoliated black Indian granite have been used as paving. Concerns about staining and marking of the stone in the high-traffic lobby have been raised and questions have been asked about some form of immediate and on-going protection of the granite surface. The application of a sealer has been suggested to provide this protection, possibly in addition to providing an aesthetically desirable “wet-look” which maximizes the desired colouration. However, there are reservations as to the efficacy of most sealers as well as to the cost-benefits associated with sealing and on-going maintenance. Experiences from other granite paving show that routine cleaning and maintenance combined with a maintenance manual that deals specifically with a range of soiling agents and their treatment is the preferred option.
The Indian granites used as paving on the Brisbane Square project have quite low porosities. Sealers do very little in the long term to protect stone from the wide range of contaminants that are available (especially foods and motorcars). Their formulations are much more suited to interior domestic use, i.e. where there is no mechanical wear, UV protection from the sun, and not subject to the effects of fluids carrying a range of dissolved substances.
Given the collective circumstances of the granite paving I would suggest the implementation of a cleaning and maintenance programme that is geared specifically towards your granite paving rather than sealing it with a product of dubious long-term value that has to be reapplied annually, and then OVER any stains or discolouration that might have appeared. Furthermore, any sealer applied to a recently exfoliated surface (that has not yet seen a significant amount of foot traffic) will be removed by the flaking of the granite surface as a consequence to its recent surface treatment. Because of the low porosity of the Indian granites sealers will in effect be topical – meaning that they will be rapidly removed from the surface by abrasion. Additionally, inevitable variations in foot traffic movements will remove the sealer differentially and possibly cause a visual contrast, i.e. tracking.
The Practice and Effects of Modifying (“Doctoring”) Natural Stone
With the ever-increasing availability of natural stone from all parts of the globe to the construction industry, as well as the home consumer, certain practices have evolved that temporarily conceal the true character of the stone. This misrepresentation is inevitably price-driven because of the pricing structure of natural stone. Some stone is more expensive than others for a variety of reasons. By temporarily modifying the aesthetic appearance of a lower-priced stone the importer or distributor stands to make a dishonest financial gain – a gain at the expense of the consumer and, in the long-term, of the industry itself.
The procedure where most of the deceptive modification to the stone is quickly revealed is in the edging. Because the edging is done by the installer and is a custom process the true colour of the granite is revealed in the edge polishing. By this stage the fabricator is already out of pocket for the slab sale, the cutting, and perhaps the installation. To limit his losses the fabricator is also likely to resort to some deceptive modification of the edge (in addition to some persuasive salesmanship) by using oils (e.g. raven) or some new-generation colour enhancers.
Irrespective of the type or style of damage that has been done to the stone the end result is an unhappy customer who wants to take some action. But how does the consumer do this? How does a customer find out what has happened to the stone and why? And to whom does he/she direct their anger – the fabricator who installed the stone but did not advise on any problems, the distributor who “just buys the stuff”, the importer who has long forgotten what the stone was and looked like, the overseas processors who might not be aware of any consumer concerns in another country, or our legislators for allowing this deceitful and hurtful practice to continue. The end user simply does not have the product that he believed that he was getting.
Investigations into the causes of failure of a Jerusalem Limestone floor
Honed Jerusalem Limestone tiles have severely pitted in a residence after only a few months of service. Although failure commenced adjacent to north-facing windows pitting progressed rapidly to all parts of the room including areas covered by rugs. The honed finish was achieved by acid-washing the original polished surface rather than through the usual methods of production. After laying the tiles were sealed as an aid to cleaning and the prevention of stains.
The problems experienced in this location have been duplicated in a number of other Australian locations and the problems associated with this variety of limestone are well known overseas. It is clear that there is a considerable variation in the quality of the limestone tiles based simply on the occurrence and abundance of the natural partings as described. Of interest is the fact that the importer of any stone into Australia is not required to provide any accurate and reliable information on its suitability irrespective of whether there are inherent problems with the material in certain situations in other countries. Decisions of whether or not a certain stone is suitable in its intended application is generally left to the architect or specifier. It is unfortunate that advice on the composition and suitability of stone in certain applications is rarely sought by architects or builders in Australia and the US.
Byne's disease revisited - investigations into the formation of a white growth on a Jerusalem Limestone floor
Honed Jerusalem Limestone tiles that severely pitted in a residence after only a few months of service were left undisturbed for several additional months in a warm, moist environment. An abundant white-coloured substance formed on the surface of the limestone tiles and within the natural limestone structures disrupting the fabric of the stone and contributing to additional spalling and eventual disintegration. The distribution of this white "efflorescence" appeared to have a gradient broadly emanating from a substantial cocktail bar housing an ice-maker. Spalled fragments of the limestone tiles exhibited an unusual, pungent chemical odour which indicated the involvement of a volatile organic compound (VOC). Several varieties of construction materials (including certain types of wood) contain such compounds and a direct link has been established historically to the disintegration of calcareous materials in museums.
The white, fibrous, crystalline growth on the Jerusalem limestone floor tiles of the residence was determined to be calcium acetate hydrate. This substance has been known for over a century to form on the surface of, and eventually totally replace, calcareous biological specimens in museums. A similar but compositionally slightly different substance has been reported as forming on archaeologically significant calcareous terracotta vases. In all instances where calcium acetate hydrate has formed there is a common link between the presence of volatile organic compounds such as acetic acid and formaldehyde, available moisture, and protracted elevated temperatures. In all previously reported occurrences the source of the acetic acid and/or formaldehyde has been type of enclosure. Wood such as premium oak emits VOC's, and both chipboard and craftwood are manufactured with glues that emit substantial amounts of VOC's (especially within about 6 months of manufacture) of the type that has the potential to cause the efflorescence. Prolonged moisture will affect the integrity of the manufactured wood products and some of the VOC's are likely to be mobilized in solution. This is supported by the presence of a pungent odour of ?formaldehyde within broken limestone tile fragments several meters from the bar. The application of acetic acid-based fluids at any stage (e.g. to remove the polished surface, to clean up after tiling, or as a general cleaning product) could also introduce a source of VOC's by the reactivation (under appropriate conditions) of any residual fluid absorbed by the limestone tiles. Additional interactions might also occur between the VOC's and any salt present in the calcareous limestone.
Stone under the microscope - Sandstones from south-east Queensland
The sandstone industry in south-east Queensland currently boasts at least 15 operators most of whom are concentrated in and around Helidon, a little township located nearly 80km west of Brisbane. Collectively, these operators account for the majority of the dimension stone being produced in QLD. Small operations relative to those at Helidon also occur around the Warwick district to the south of Helidon, Murphy’s Creek between Helidon and Toowoomba, and another quarry and processing facility has recently been established between Beaudesert and Boonah.
Historically, the use of QLD sandstone for serious construction commenced in the 1860’s with quarries at Albion providing stone of variable quality. Westward extension led to the commencement of quarries at Goodna and Woogaroo and although coarse-grained the sandstone saw use in some prestigious buildings, e.g. Parliament House. Brownish sandstone was discovered near Helidon before the turn of the century and many quarries there have produced large volumes of stone for domestic and export use. The University buildings at St Lucia and City Hall are excellent examples of the durability of this stone.
Today the sandstone industry is quite mechanized and with crawler tractors, diamond wire saws, large diameter toothed blades on excavators, and Korfmann chainsaws extracting the bulk of the stone.
The commercial sandstones of south-east QLD were deposited as fluviatile sands during the formation of the Clarence-Moreton Basin. The timing of this deposition (Early Jurassic to Late Triassic) is close to 200 million years (which corresponds roughly with the appearance of the early dinosaurs).
Because sandstone is formed by the deposition of eroded, fragmented rock particles in continually changing hydraulic conditions, and then modified by post-depositional processes such as lithification, diagenesis and pore fluid activity it is hardly surprising that there may be many varieties of sandstone within the one quarry. Not only are there variations in structure, texture, and composition but also in colour. In addition, appearance can also be controlled during processing by the way the sandstone is cut with respect to its structure. A number of the quarries have a highly distinctive, speckled brownish variety that distinguishes Helidon sandstone from all others of the world. In Sharp contrast, the principal sandstone from near Beaudesert, about 80km south-west of Brisbane is a remarkably uniform medium-grey coloured stone that is almost indistinguishable in appearance from the sandstone Pietra Serena that has been quarried for over 400 years in Tuscany, Italy.
.....The application of sealers to sandstone paving is one area that tends to have problems. Home-owners and commercial operators are frequently advised by the salesmen to seal sandstone around pools and decks, especially in QLD. Within months there is a frequent incidence of failure with the sandstone delaminating, the arrises spalling or the surface pitting. Usually the quality of the sandstone is brought into question; however, failure is mostly due to the contrasting physical properties of the sandstone skin containing the sealer, or the migration of salts through the sandstone and meeting a barrier (the sealer).
Stone under the microscope - Absolute Black
Absolute Black is both a specific and general term used in the stone trade for a fine-to medium-grained igneous rock that approaches a black colour when highly polished. Because of the superior geotechnical characteristics of this type of stone coupled with its rarity relative to other granite varieties Absolute Black is perceived as a prestigious product. For these reasons the main applications of Absolute Black are in the monumental trade, for modern and/or prestigious internal flooring, and for kitchen tops. Although the initial Absolute Black arguable emanated from South Africa and was given the Italian name of Nero Assoluto other countries have adopted the anglicised term to differentiate this type of stone from other dark granites. Because of the strong mineralogical and chemical similarities that characterize this type of stone the following discussion will incorporate most of the Absolute Black granites of the world. India, China, and South Africa produce the majority of Absolute Black but there are contributions from Zimbabwe, Uruguay, Brazil, Sweden, United States, and Australia. Australia is littered with numerous small deposits of such black granite but in many instances the size of the individual resource is too limited, the location of the resources too remote, and the geological structures too demanding to make exploitation viable and sustainable. Of the 30 quarries from which this stone type was extracted in the Kimberleys none continued for more than a short period.
Stone under the microscope - Black Galaxy
Black Galaxy is the trade name given to a generally medium-grained blackish stone that displays small, conspicuous reflections. Because of the rarity of stone with such reflective features Black Galaxy is perceived as a prestigious product. Its main applications are internal but there is an increasing tendency to also use this stone externally. It emanates from near the village of Semakurthy in the Ongole region of Andra Pradesh in southern India. Of the 30-40 quarries from which this stone type is extracted only about 10-12 contain stone of export quality. The proliferation of quarries is attributable to the low relief, sheet and residual boulder formation of the stone.
A polished slab or tile of Black Galaxy shows many of the characteristics of this granite including colour, texture, and structure but resin applied to the samples inspected conceals the degree of alteration and true character of finish. The colour is predominantly a black with conspicuous flakes of a bronze-coloured mineral providing a sparkling effect depending on the angle of light reflectance. There is a degree of granularity because many of the bronze-coloured crystals are of similar size and have a similar degree of reflectance. Some variation in the abundance of reflective bronze-coloured crystals on different sides of a thick stone suggests a structural or magmatic flow orientation. Contrary to popular belief the sparkling effect is not due to the presence of large flakes of mica.
The surface of the tile contains a multitude of microfractures which is probably the reason for the resining process in order to conceal some of these physically undesirable features. There are also small pits and a surprisingly high abundance of sulphide. The darkness of the rock effectively conceals any alteration that might be present.
Stone under the microscope - The Pearl Granites
Of the many natural products pearls have traditionally attracted considerable attention for their rarity and aesthetic appearance. Pearls without blemish have symbolized perfection since ancient time. They were so highly esteemed in classical Rome that permission to wear them was restricted to persons of high rank. The Roman statesman Pliny considered pearls as "the richest merchandise of all and the most sovereign commodity in the world".
The key factors to the desirability of the pearl are iridescence and translucence. Added to this is its rarity and fragility requiring delicate workmanship and maintenance to retain its splendour and value.
Because of this traditionally high regard for the intrinsic characteristics of pearls it is little wonder that the occurrence of another natural product with similar characteristics commands an equally esteemed status in the field of stone. History has it that the "Pearls of Norway" remained undiscovered until an exhibition at the World Fair in the 1890's called for each participating country to submit and display the two most prestigious varieties of building stone produced in each country which were then to be judged by a panel of architects. Embarrassed, (because Norway only quarried one variety of stone at the time - presumably marble) an urgent request was sent out to a scientist to find another type of stone for this exhibition. Having spent much of his time around the Larvik region of Norway, Broegger submitted a larvikite to the government for the event. It is recorded that a variety of Blue Pearl from Larvik won first prize. It has maintained its high stature since that day.
Clearly cashing in on the prestige afforded by the Norwegian Pearls numerous stones containing some iridescence in the alkali feldspar have been renamed and/or marketed as a "Pearl". Black Pearl is a variety that is widely distributed. The Black Pearl that is now freely available is quarried in India and exported worldwide whereas the original Black Pearl from Sierre Leone, West Africa has virtually disappeared and could not be procured for examination. The Indian Black Pearl is a mineralogically, texturally and structurally complex rock containing abundant alkali feldspar, a scattering of plagioclase feldspar, and minor quartz. The ferromagnesian minerals are very enriched in iron and include subequal amounts of calcic pyroxene, ferrohypersthene, ferro-edenite or hastingsite, plus minor possible annite (mica).
Apatite is conspicuous and locally abundant as moderately large crystals. Modally it just falls into the syenite field, adjacent to monzonite. Textures show that this type of rock has had a long and complex history. Deformation textures are common and there is good evidence for both high-temperature and subsequent low-temperature thermal events that have modified the original mineralogy. Intercrystalline micro-fractures are very abundant as are veinlets of chlorite through the alkali feldspar. These veinlets are largely responsible for the dark green colour together with the very dark green ferromagnesian minerals. Both feldspars contain an abundance of tiny, oriented inclusions, commonly in three directions, and of different compositions in the respective feldspars. It displays little or no iridescence, labradorescence or schiller effect so should not be part of this "family". An interesting pearl granite being exported from Finland is Lilac Pearl, a gneissic granulite containing large feldspars and a strange mineral called nuumite. Previously discovered in Greenland this mineral is commonly known as Greenland opal.
Other pearls available on the world market are prefixed with the following: silver, golden, green, pacific, aqua, brown, lunar, yellow, and oyster. For something different just swap the names to give pearl green, pearl flower, pearl red, pearl white, pearl grey, pearl star and even pearly green. When unable to categorize the stone just call it grey blue pearl. Many of these "recent" pearls emanate from Asia. The calcareous category of stones also has some pearls, such as Sinai pearl and Sicilian pearl. Even Australia has a variety known as Snowy River Pearl. This is quarried near Omeo, NE Victoria, and is a spectacular granitic rock of overall pinkish-brown colour containing large to very large phenocrysts of prismatic, randomly oriented alkali feldspar crystals that display a strong bluish iridescence in certain orientations.
Note on some "tricky fractures" in Volga Blue Granite
Abundant hairline features in kitchen benches manufactured from slabs of 20mm thick polished Volga Blue granite (selected by the client) have been interpreted by the client and his representatives as structural defects likely to lead to future problems. Additionally, there has been a suggestion that these hairline features could represent a potential health risk by harbouring pathogenic bacteria.
Volga Blue is the trade name for an exceptionally coarse-grained, plutonic rock quarried in the Ukraine. Crystal size is measured in centimeters rather than millimeters and it contains highly distinctive, very large feldspar crystals displaying a bluish opalescence. The textural rarity coupled with the schiller texture of the feldspar places this rock in the "upper class" price bracket. The rock appears to be fresh geologically with very little obvious weathering of the minerals. This mineralogical freshness is borne out by a high-pitched "ringing" sound when struck. Moreover, the quality of the sound is also an indication of its integrity. Any substantial discontinuities in the rock whether textural, mineralogical or structural, would result in a noticeably duller sound.
Quarrying of this granite is carried out by drilling vertically and horizontally. Primary blocks are extracted by a combination of expanding cement (vertical faces) and lifting the floor with an air explosive. Although this technique is widely used in granite quarrying and can be reasonably successful on certain rock types the technique can lead to problems with brittle granites. Inspection of many slabs of Volga Blue reveals the damage that has been done by both the expanding cement and the explosive. Much of the damage is directly attributable to the rock's freshness and coarse grainsize (i.e. brittleness) and, unfortunately, the reduced recovery of unfractured blocks translates to elevated costs for the end product. After the blocks are cut and polished (usually in Italy) slab inspection generally separates the good product from one not suitable for further processing. Some operators will attempt resin fillings to hide structural blemishes but these are obvious to a 'trained eye'.
Building Stones of the New Parliament House, Canberra
The New Parliament House on Capital Hill is an architectural form intended to express our national, cultural and political identity, and was designed to blend into the natural landforms and the city of Canberra. The distinctive geometry of the building includes impressive curved walls and incorporates some design aspects historically intrinsic to the development of Canberra.
Stone is a particularly fundamental and integral part of the building constituting much of the exterior and interior. Of the stone used about 90% is Australian. The remainder came from Italy (mainly the marbles) with a small proportion from India, Brazil and Europe (mainly for the Aboriginal mural).
In each location the stone was selected to be:
- mutually compatible with other natural and man-made materials,
- durable,
- the most appropriate aesthetically for individual locations,
- and indigenous, if available commercially
Granite dominates the stonework because of its recognized durability and compatibility with associated structures. Though not restricted to the inside of the building the marbles do tend to be more abundant in interior applications which are traditionally considered to be aesthetically more demanding.
Investigations into the composition of arkalite
Paving/flooring material used extensively in parts of St. John's Cathedral, Brisbane, is pitting and spalling in a number of places. This material is basically a reconstituted stone/cement product that was specified by a British architect and introduced into Australia for the Cathedral in 1904. By establishing the composition of this man-made product it is hoped to find, or manufacture locally, a compositionally similar product that is a satisfactory match to the existing floor.
This is a very unusual, composite, man-made product. Most of it has been derived from waste slag materials produced within a blast-furnace ladle during iron smelting operations. The glass has clearly been added at a later stage and the quartz appears as a possible impurity introduced during manufacture.
There are no clear indications as to how this material was produced. The layering and surface finish suggests some form of hot-pressing or hot-rolling after mixing with the carbonaceous and probably gypsiferous matrix. Nearly all the components are basically anhydrous and the majority of slag minerals are seriously silica-deficient. This provides some evidence as to why there has been no hydration of the glass nor the presence of an alkali-silica reaction within what was thought to be a cementitious matrix.
Duplication is likely to be tricky even though all the ingredients can be readily obtained. Crushing and blending is straight-forward but the moulding process is not understood. To produce the strength for a paving product it would be necessary to add a flux such as gypsum. This could explain the formation of jarosite (an iron sulphate formed by reaction with both the freely available iron and a calcium sulphate). The source of the potassium is unclear. Steam could possibly provide the driving mechanism for the required reactions to solidify the material (similar to the manufacture of man-made sandstone bricks) but it is more likely that it would have to be baked.
Report on the appearance and performance of the recently constructed National Police Memorial, Canberra, ACT
Two Chinese granites, (second grade) Shanxi Black and PFGE0010 light grey, salt-and-pepper granite, were selected and specified as the construction stones for the National Police Memorial. Both granite varieties are staining (for different reasons). The black granite paving and panels covering the shards are discolouring due to rust. The “black” concrete shards are becoming very discoloured by white efflorescence due to the quality of the construction. Efflorescence is also emanating from joints between the inscribed black granite plates surrounding the shards. A large proportion of the sanded grout joints of the shards show hairline fracturing which is also causing separation of the granite panels and even lateral displacement. The white granite is discolouring because of high inherent porosity, the effects of sealing and the continuous ingress of water below the tiles.
......It is concluded that the specifications prepared for the construction of the National Police Memorial were deficient in a number of respects, particularly in stone selection (resulting in conspicuous rusting) and in construction methods which did not preclude the entry of water into the shards though the stone panelling (leading to widespread efflorescence) and into the sub-tile stratum beneath the white granite (causing eventual discolouration).
To award a stone contract to a company that is not experienced in the many important facets of stone selection, stone supply, stone use and stone construction is regrettable and should not have happened. The results speak for themselves. Whilst the present contractor might have been somewhat cheaper in his tender than the more experienced stone companies the replacement or rectification costs will undoubtedly be considerably more than the other original tender quotes.
It has also been noticed that little or no independent expertise on natural stone is sought by the authority to assist them in the pre-tender stage and/or in the evaluating/awarding of tenders that have a natural stone component. There are many aspects relevant to any stone construction where specific advice should be provided so that complex situations such as this current one do not arise. Drawn out contractual and legal disputes could be avoided with the appropriate expertise.
The condition of the National Police Memorial presented above is poor and essentially beyond repair. Either the condition of the stonework in the memorial is accepted with its many deficiencies (but ones that will deteriorate further) or it is basically replaced using high quality stone and constructed by professional stonemasons.
Orbicular granite from Mt. Farmer, Western Australia
Orbicular granites are spectacular geological enigmas. They occur from place to place as small pods, trains, bands, lenses, pipes and patches, not uncommonly along or close to margins of granitic intrusions. They occur on all continents in rocks of many ages. Orbicular granites are so fascinating geologically because of the structural complexities and variations in mineral composition within and between individual deposits. Significantly, even though orbicular structures have been recorded in many rock types from a wide range of physical and tectonic settings, no two orbicular granite occurrences are alike.
......One significant feature of the 2.6 b.y. old Mt. Farmer orbicular granite is its overall freshness. In this aspect it is unlike most orbicular granites which are characteristically substantially altered by the large amount of magmatic water associated with its formation, or by subsequent hydrothermal activity. This freshness translates to a polished finished quality which is at least very good.
…….Many factors contribute to a compelling and instant appeal for this exotic stone including its freshness, variation in orbicule morphology, variation in mineral composition from one orbicule layer to the next and from orbicule to orbicule, variation in the ratio between orbicules and “groundmass granite”, and the intimate relationship in places between the orbicular granite and commonly associated post-emplacement features. Add to this a scattering of large gemstone quality titanium minerals and very rare pockets of complex sulphide intergrowths. The nett product is a spectacular rock of unsurpassed 3-dimensional visual effect guaranteed to promote endless conversation, argument and speculation.
Specific details regarding the use of beige/light-brown granites
All beige or similarly coloured crystalline rocks have those colours for very good geological and mineralogical reasons. They contain small amounts of hydrated iron oxide (usually within the feldspar) which ranges in colour from earthy yellow through to brown. The reason for its presence is due to a remobilization of very small amounts of iron-bearing fluids through the granite by late-stage or post-emplacement hydrothermal activity. The majority of the dissolved/remobilized compounds are derived from iron-bearing trioctahedral micas (biotite, annite) and to a lesser extent iron sulphide and iron oxide.
Because of the presence of the hydrated iron oxide the beige and yellowish-coloured granites cannot be exfoliated (flamed) without changing the state of crystallization of these poorly formed hydrated minerals. With the heat of exfoliation exceeding 1000 degrees C haematite is formed in small crystals and globules from the hydrated iron oxide and this changes the colour to pinkish.
Because of the elevated rate of water absorption (around 0.4%) and their unusual chemistries these granites need to be treated in ways different to most other granites. They are not meant to be cleaned with acid nor saturated with water containing alkaline compounds. Such chemicals will “burn” this type of stone. Expert advice should be sought on the use of these specific stone varieties.
On the Viability of Granitic and Doleritic Rocks for Dimension Stone in the west Kimberley area, north Western Australia
A number of efforts over a few decades have been made to extract several stone varieties from the Kimberley district of W.A. Some granitic and metadoleritic rocks have been targeted because of their unusual and appealing character. For various reasons the activities were eventually abandoned. The granitic rocks occur as large whalebacks and a number of faces and quarries have been worked. Feedback from all the stone processors indicated that the stone was damaged by blasting or by stress, be it natural or man-made. More limited damage was also done to the granite immediately adjacent to the thermal channeling although there is a possibility that fracture propagation may have extended beyond - along the foliation plane and also because of the presence of considerable inherent stress in this granitic rock variety. Stressed rock will relieve its stress in a number of ways and is a serious consideration in terms of stone integrity and quality.
The metadoleritic rocks were also examined to gain some indications of extractability and therefore viability as a high-class product. These metadolerites occur as dykes that are intrusive into metasedimenats and gneissic granitic rocks. There have been about 30 locations is this region where some form of quarrying activity has taken place. Most operations have been unsuccessful commercially for a variety of reasons, the most common being stone quality and consistency.
An examination of the dykes focused on joint frequency, joint spacing, healed joints, veining, colour, and general textural homogeneity. A serious consideration to the commercial viability of the dolerite dykes is the joint spacing. Clearly, prolonged exposure to the elements has resulted in the formation of numerous vertical and horizontal joints. Their immediate effect is to broaden the dyke with displaced material and give a false impression of the true width.
It has been suggested numerous times (mainly by geologists) that the dykes should broaden with depth just below the point of exposure. When drilling and excavating has been done this premise has been shown to be totally erroneous. Any suggestion of broadening is nonsensical and extremely irresponsible when the overall environment of their formation is considered. These dykes have intruded through possibly 8km or more of granite and other country rocks and they are now exposed only because the landforms have reached a certain stage of denudation. The attitude of the dykes may well (and should) vary in their shape and form over a kilometer scale but not on the scale of say 50 to a maximum of 100 meters involved here.
It must be emphasized that there are many more dolerite dykes that can be evaluated. Perhaps with more specialized expertise some dolerite can be found that are more amenable to quarrying and have fewer mineralogical problems. Similarly, the region has a wide spectrum of intrusive and metamorphic rocks that could be of special interest to the world dimension stone industry.
The Prospectivity of Building Stone in New England
Building stone is a broad term encompassing many forms of stone used in some type of construction. The history of its use goes back to the Egyptian monuments followed later by the ancient Greek and Romans and subsequent civilizations (e.g. Incas). Although enormous quantities of roughly hewn stone are still used globally for many purposes its use tends to be strictly local. In contrast, there is a huge international trade in another form of stone – dimension stone. This is the form of stone that is produced to a set dimension and finished in numerous ways for that aesthetically driven appearance. Dimension stone touches more people in everyday life than the majority of high profile commodities. Millions of people have daily physical contact with it - walking on it (floors), driving over it (paving), leaning on it (banks and kitchen tops), playing on it (billiard/pool tables), eating off it (hot rock plates) and providing memories of the departed (gravestones).
Any stone that is separated from its last natural source and capable of being and intending to be dimensioned can be a dimension stone. However, to be a commercial dimension stone there is an implication of physical and chemical durability if it is be used in construction because constructions have design lives. In addition to durability the stone must be available in sufficiently large amounts and have a consistency in texture, structure and appearance (colour).
These fundamental characteristics together with the required strengths, capacity for water absorption, and a stable mineralogy generally dictate the type of application for that stone, and in turn this determines whether it is commercially viable. In the past the proximity of a dimension stone to a population centre was important but modern processing and transport techniques allow stone to be sourced from all countries of the world. Ironically, a local quarry at the edge of town may now not be a viable proposition for sourcing stone for construction.
Because stone is a construction material there is a heavy emphasis on the quality of its natural characteristics. Engineers require a plethora of information before committing to construction especially because of its potential small-scale variability. Numerous methods of testing are available and numerous standards have been developed in a number of countries to measure and control these natural characteristics. The stone is subjected to petrographic analysis, compression, flexion, rupture, absorption, expansion, to name a few and may undergo more rigorous scrutiny in laboratories to test for deleterious minerals by X-ray diffraction, freeze-thaw resistance, abrasion resistance, chemical composition, radio-activity and radon evolution, and pulse velocity measurements. Depending on the type of surface finish and its eventual intended application it is also subjected to slip tests and stain tests. It may also be coated with a range of synthetic products.
In addition to the intense laboratory scrutiny field inspections of a stone resource are equally as important when determining commercial viability and product acceptability. It must be possible to extract the stone from its resource, consistently, to a fairly set size, profitably, and without damage to the product. Natural features and flaws must be avoided and subtle variations must be recognized. Natural or induced fractures are particularly detrimental to an operation because of the down-the-line financial ramifications.
Naturally different stones have different characteristics and requirements, have different applications and require different expertise and machinery for extraction. On top of this there are the fickleties of sales, weather, machinery performance, landholder demands, environmental restrictions, government rules and regulations. It’s a wonder that anyone bothers at all in getting a stone resource off the ground.
Counter cleanliness in the US - beware the numbers of poor science
A recent article in Today's Homeowner Magazine entitled "For counter cleanliness - granite is the way to go" highlights some of the ignorance associated this subject. The article was based on a study undertaken by Dr Snyder at the Hospitality Institute of Technology and Management at St Pauls in Minnesota, USA, in which he conducted tests to measure the bacteria resistance capacity of six countertop materials such as stainless steel, granite, plastic laminate, tile, concrete, and wood. The test involved the contamination of each top with 2 billion Escherichia coli bacteria. The cleaning procedure which followed involved washing and rinsing each surface with soap and water followed by sanitizing with a vinegar-water solution.