Tuesday, 31 August 2010 19:37

The 411 on Natural Stone

Written by Angela S Colley
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Natural stone is a very popular material used in both interior and exterior spaces. Depending on the stone, it is important you know what works best in your installation. Natural stone is harvested from the earth and there are 3 types:  Sedimentary, Metamorphic and Igneous. All three can be composed of either calcareous (CaCO3) or siliceous (SiO2) material.

Let’s go back to the basics and review geology. If you want to bypass this section, How‘s Stone Made, go directly to  Types of Stone.

How‘s Stone Made
Sedimentary Stone is formed from the earth's surface sediment layers that have settled and accumulated over time.

Metamorphic Stone is formed deep beneath the earth's surface, from high temperatures and pressure from rock layers above it.

Igneous Stone is formed through the cooling and solidification of magma or lava. Igneous rock may form with or without crystals, and either below or on the earth’s surface.

The following table shows the relationship between the stone type and its chemical makeup.

  Sedimentary Metamorphic Igneous
Calcareous Limestone
Travertine
Onyx
Marble  
Siliceous Sandstone Slate
Quartzite
Serpentine
Granite

Types of Stone
Limestone contains fossils or shell formations. This stone has a grainy appearance, and may contain streaks or spots. Beware, limestone has iron deposits and therefore will rust over time due to the iron content. If used in humid spaces, the rust stains will become more prominent. If you want that natural patina, rust stains will add character to the stone as it ages. Limestone dissolves easily in acids and is not sensitive to heat. Limestone surfaces should be sealed to resist chemical damage and staining. To maintain limestone, vacuum or sweep, and wash with soapy warm water. This stone can be used in kitchens and bathrooms, on floors, walls, countertops, backsplashes, basins and sinks.

limestone amerelo de negrais1

Travertine is fine crystallized stone formed via hot springs. It is a land based stone and generally includes holes. It is great for flooring but the holes should be filled. This stone will break over time due to the holes in the stone. Travertine is great for floors and walls, inside and out doors.

travertino romano noce

Onyx has cryptocrystalline texture and is generally translucent. This stone is usually formed from cold water in caves. It is sensitive to chemical and mechanical attack like wine and lemon juice. It also has low abrasion resistance. Onyx can be used for bathroom countertops, back splashes or sinks. Because of its translucent character, back lighting the slab creates drama.

green onyx

Marble is a metamorphic rock that is formed when calcium from shells and bones of prehistoric life, combines with carbon dioxide from water.  The color of the marble depends on other mineral content; the presence of hematite creates red marble, limonite creates yellow, serpentine creates green and diopside creates blue. Marble does not perform as well as granite or slate; it is a softer stone. Though marble can withstand heat, it can stain from acids, and therefore should be sealed. Marble is suitable for interior fireplace surrounds, backsplashes, shower surrounds, sinks, bowls, basins and tubs. If used as a countertop it must be resealed every few years. Polished marble, when wet, is slippery and therefore not suitable for floors.

marbel arabescato orobico rosso

Sandstone is a sedimentary stone that consists of silt or clay and is very porous. It has the same properties as limestone, and should be treated in the same manner.

sandstonr fossil1 teakwood sandstone2

Slate is a compact micro-crystalline stone that is formed from shale deposits. This stone is fireproof, is non-porous, repels water, moss and fungus, can resist acids and other pollutants. It is suitable for interior floors, walls, showers and fireplace hearths and surrounds. Outdoors, it can be used for pavers for paths and patios, retaining walls, pool and spa surrounds, landscaping and water features. It comes in a variety of colors from black to deep gray to greens and reddish browns.

slate raja red

Quartzite was originally sandstone that converted into quartzite through heating. Quartzite is very durable and resistant to chemical weathering. Quartzite is used often for wall covering, roofing tiles, flooring, and stair steps.

quartzite silver grey

Serpentine is a very durable hard stone that performs well outside. It is often mistaken for marble.  It has a magnesium-silicate base and has better resistance to acid and abrasion than marble. This makes serpentine a good choice for kitchen counters and exterior applications. It is ideal in foyers, bathrooms, floors and hearths.

serpentine stepping stone serpenti

Granite is a granular, crystalline rock made up of 10% to 50% of quartz. It is one of the hardest and denser stones, resistant to abrasion, chemicals and weathering. Granite can be polished to a smooth finish making it an ideal hygienic surface for kitchen countertops and backsplashes. Granite is also popular for making sinks, lining showers walls, window sills, hearths and fireplace surrounds. Granite is also popular for exterior use as garden pavers, benches, fountains and building facades. Granite is porous and will stain if not sealed.

african rainbow granite1

Popular Stone Finishes
Polished – high gloss giving a mirror-like reflection.

Honed – very smooth flat finish.

Flamed – textured matte finished.

Sawn – cut with a saw with no additional finish.

Sanded – textured sand blasted finish and slip resistant.

I know this is a lot of information to digest, but my intent is to help you decide on the natural stone that works best for you. Good Luck!!!

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Angela S Colley, ASID|CAPS

D# 5487 • IB# 26001097

A C Styles Designs, LLC

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