Frequently Asked Questions
- IGNEOUS – those formed by the cooling and solidification of molten magma.
- SEDIMENTARY – rocks formed by the accumulation and compaction of fragments from pre-existing rocks which have been disintegrated by erosion; organic debris such as shell or coral fragments; or materials dissolved in surface waters or groundwater, which is precipitated in conditions of over saturation.
- METAMORPHIC – rocks formed from pre-existing rocks of any type, which have been subjected to increases of temperature or pressure or both, such that the rocks undergo recrystallisation.
a. IGNEOUS – Granite, Basalt (Bluestone), Trachyte.
b. SEDIMENTARY – Sandstone, Quartzitic Sandstone, Limestone.
c. METAMORPHIC – Marble, Slate, Quartzite, Greenstone.
Many people believe that natural stone is non-porous. In fact, while many natural stone products do offer high porosity values and are relatively easy to clean, marble is not one of them. The majority of marble floor and bench or counter top installations should be protected by the addition of sealer. For more information on the subject of sealing stone read Stone Sealer – Function, Facts, Fallacies which appears in our e-digest.
The majority of wholesalers, resellers and processors of natural stone bench or counter top materials will allow prospective purchasers to view their stock so that purchaser can select specific slab(s). With regards to tile one has to understand that each tile is likely to be completely different in terms of viewing.
Therefore, it is advisable to select tiles, as work progresses, from a variety of boxes, thereby ensuring that one obtains a random look, that fully illustrates the beauty of the chosen product.
Marble is more commonly employed as bathroom vanity top material, however many home owners prefer the more natural veining and open appearance of marble, to the denser, less porous granite.
Marble can be successfully sealed using proprietory sealers available from a variety of companies including ASAA members Aqua Mix Australia, CDK Stone (Lithofin products) and Spirit Marble & Tile Care.
Remember that marble scratches more easily than granite, so if you are cutting or preparing food use a work top protector. Marble can certainly be used on kitchen bench tops, but granite is probably a safer bet.
Engineered stone (also known as reconstituted, re-composed agglomerated and synthetic stone) is manufactured from a mix of stone aggregate chips (most commonly quartz or marble, but also igneous rocks such as granite and basalt); mineral fillers (generally the ground aggregate); a resin binder (typically an unsaturated polyester); pigments and additives. Tiles are typically formed using a vibrocompaction process, where applied vacuum minimises any porosity, usually reducing the water absorption to much less than 0.4%. There are many different kinds of polyester resins, with different viscosity, colour and hardening time. Tile curing may be accelerated by using ovens or steam. Some tiles are given post-curing heating treatments to increase the degree of cure.
Since there are no standards for adhesive fixing of engineered stone tiles, they tend to be fixed according to ceramic tiling standards, using adhesives designed for fixing ceramic tiles. Tiling codes of practice have evolved from an empirical basis, where what was found to work was adopted, and attempts were made to eliminate those practices that were associated with failures.
Some home owners and interior designers prefer engineered stone, because while the material has the appearance of natural stone, it is totally reliable in terms of colour. A builder using the material on bench and vanity tops in a new residential development can be assured that each piece is identical and if a client requires a new bench top a year on, that piece will also be the same.
The products enviable low water absorption values, generally less than 0.4%, and the wide range of available finishes are other factors in the products favour. The growing popularity of engineered stone is entirely understandable.
However for those in search of an entirely natural product, that also offers good porosity values, granite may well be the answer.
While engineered stone is fine inside, its colour can change in sunlight. No product can be totally guaranteed against splitting, cracking or staining. Engineered stone is a fine product, but it is no exception to the rule.
In short, black granite should not fade. Quality black Australian granite does not. However some producers in Asia have been known to artificially darken the colour of the product by adding dye or oil to the surface.
You can check if the product has been altered by putting some Acetone on a clean rag and applying a small quantity of the liquid to the surface of the granite in question. If you spot any residue substances on the top of the material, simply reject the material. It will almost certainly be a foreign product, frequently given an Australian or classic name.
The most common kind of stain is frequently described as halo staining. In the majority of cases Alkaline-tainted rainwater is discovered to be the culprit. Issue no. 6 of Discovering Stone will contain a major feature on this problem, which is normally the result of frequent saturation of sand and cement bedding materials in bathrooms and other wet areas, rather than a single cycle of wetting.
For more information read Peter Hartog’s informative feature in Discovering Stone.
In theory marble, which is softer than say granite, is more likely to scratch. However most stone is subject to some degree of scratching. For that matter so are most other floor coverings, even the most robust ceramic tiles.
Prevention is better than cure, so wear appropriate footwear, wipe your feet on a good course doormat, better still remove your shoes and with them the risk of a small pebble from being scratched and scraped across your floor.
Sweep the floor with a soft broom, thereby removing any grit, dirt or other contaminants. Yes, stone can be scratched, but by using a little common sense, the risk can be greatly reduced.