Natural stone is popular in Californian countertops. There are three (3) basic types of rock:
(i) Igneous: Crystalline solids formed directly from the cooling of magma, they are named based upon composition and texture (crystal size)
(ii) Sedimentary or Secondary: When igneous rocks are covered by a thin veneer of loose sediment and the debris get compacted and cemented together, seocndary rocks are the result of the accumulation of small pieces broken off from pre-existing rocks. They may be clastic (lithified by compaction and cementation), chemical (upon evaporation of standing water) or organic (especially on the sea floor)
(iii) Metamorphic: Formed when rock is moved into an environment in which its intrinsic minerals become unstable and dysequilibrated, in most cases arising from burial with tremendous rises in temperature and pressure, as seen in slate, shist, gneiss, and marble.
Beyond the aesthetic of a rock type (veining, crazing, texture, culturing), there are simply two (2) factors that are key: hardness and durability in the face of a chemical attack.
Hardness
A countertop needs to be harder than a knife and resistant to incidental chipping. Igneous and metamorphic rocks are harder and more durable. Granite is made of silicate (mostly silicon and oxygen, tough stuff) ; marble is made of calcium carbonate (soft stuff); soapstone is talc (the softest mineral of all). Granite passes all the hardness and incidental bump tests.
Chemical resistance
Marble or granite? Calcium carbonate will dissolve in water over time and thus the finish will dull but granite will persist longer.
Granite, an igneous rock, is cost-prohibitive, acid-stainable, and requires buffing and protective sealing every six (6) months. Granite needs to be sandblasted from the earth with a diamond-edged cutter and the good varieties need to be imported from Eastern Europe or South Africa. Granite shows particulate material from different minerals embedded within, has veining similar to marble, is hard, durable and practically scratchproof. It is easily cleaned owing to its low porosity but is not forgiving of many oils and acids in the busy kitchen. You need to wipe up wet spills immediately, especially acidic liquids like citrus juice, alcohol or pop. All cleaning products used should be strictly pH neutral and you may not use harsh chemical or abrasive cleaners. Placemats must be placed under hot dishes to prevent unsightly fissures and cracks.
Natural stone quartz surfaces are emerging as a viable alternative. Cambria is elegant and non-absorbent, thus reducing the potential for bacterial overgrowth. It is maintenance free andimpervious. It is better suited for bathroom shower surrounds and vanities, as it has a clean, stark and somewhat sterile look. Silestone is clear, radiant and solid. Its pre-polished surafce requires no sealing unlike granite, marble and limestone. Its scratch- and scorch-resistant properties ake it attractive for kitchens and fireplace surrounds. Only diamond, sapphire and topaz (all natural minerals) are harder than quartz (which is a 7 on the Mohs hardness scale, where diamond is a 10). Clean with soap and warm water.
Like granite or salte, Soapstone is a talc quarried product from Vermont or Brazil. it is natural, non-porous, and will not stain or be affected by water, chemicals, acids, or temperature extremes. Before initial use, darken it with a thin film of mineral oil and repeate once annually. As a metamorphic stone, it is soft, warm and organic, and thus unstained by foods and oils.
Pyrolave is enameled lava from volcanic flows in Volvic hardened at 1800F with a natural hard finish. Created in 1987, it is now located in Castelsarrasin. Every countertop is made to order and repeated use enhances the presence of delicate crazings. Its inherent hardness makes it one of the most resistant to shock and scratch. It is unaffected by flame, and is impermeable to water, greases, alcohol and cleaning products. Use a wet sponge and light detergent to clean.
Daily care for stone countertops
* Commercial natural stone cleansers are available at Home Depot.
* An alternate is a mild pH neutral dish detergent such as Ivory.
* Use paper towels or disposable cloth to wipe down after contact with food.
* Occasional use of 50% bleach in water may help disinfect but can cause etching.
* Wiping off acidic (citrus juice, vinegar, wine) and oil-based (cookingoil, grease, butter, margarine) will preclude staining or compromising the finish
* Do not use tile cleaners, window cleaners, degreasers, abrasives or anything containing ammonia. Cosmetics like shaving cream, lotion, makeup and perfumes will stain.
Specific Stone Care
Granite
Scratching: Use a cutting board
Staining: Wipe immediately. Seal with stone impregnator. Do not use ammoniacals.
Burning: No burn marks but intense heat absorption on surface will leave it hot.
Marble
Scratching: Care like for wood. Do not use in kitchen. Use trivets, placemats and cutting boards.
Staining: V susceptible. Seal with penetrating sealer to prevent absorption. Ugly water stains.
Etching: Calcareous and acid-sensitive. Dull and changed texture over time inevitable.
Burning: Has potential to burn.
Limestone
Scratching: Same as marble. Will be scratched by china and ceramic.
Staining: Most porous and susceptible. Seal pre-installation. Periodic resealing.
Etching: Acid-sensitive. Use approved limestone cleaners
Burning: Has potential to burn.
Travertine
Scratching: Soft as it is a type of limestone.
Staining: Reseal with penetrating stone sealer
Etching and Burning: Same as for limestone.
Soapstone
Scratching: Buff with fine grit 300 sandpaper. Touch up with mineral oil. Easy to chip or crack.
Staining: Impenetrable.
Oiling: Regular oiling to keep consistent color. (week 1: 2 applications; wks 2-4: 1 per week; wks 5-9: 1 per two weeks; monthly through 18 months; oil twice per yr after initial year of care)
Wipe mineral or linseed oil over entire surface and wipe off with clean cotton cloth, store for later touch ups or buffing out scratches.
Burning: Resistant to burn but will absorb heat.
