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        FACTS ABOUT STONE

  
     
 

Maintenance is an important consideration in your choice of stone for any application, especially when it's indoors and you look at it every day.  Knowing something about your stone's history will give you clues about it's maintenance requirements and the likelihood that you'll still love it in 25 years!  

Stone is natural and may have adverse reactions to certain cleaning chemicals and procedures. Most stones are also natural alkalis and so are dirt and soil; therefore, stone and dirt are attracted to each other which often makes cleaning very difficult. This makes the proper selection of cleaning procedures and chemicals for stone very complex.

 

  
 

 

  
  Types of Stones:   The familiar stone types that are used today are identified through five categories:
  1. SEDIMENTARY:  Limestone, Sandstone, Soapstone, Fossilstone, Travertine
  2. METAMORPHIC:  Marble, Slate, Serpentine
  3. IGNEOUS STONE:  Granite
  4. SCHIST:  Pietra di Cardoso
  5. MAN-MADE. 

SURFACE TEXTURES

 

  
 

 

 

 I. SEDIMENTARY stone came from organic elements such as glaciers, rivers, wind, oceans and plants. Tiny sedimentary pieces broke off from these wind elements and accumulated to form rock beds. They were bonded through millions of years of heat and pressure.
  • LIMESTONE: Mainly consists of calcite. It does not show much graining or crystalline structure. It has a smooth granular surface and varies in hardness. Some dense limestones can be polished. Common colors are black, grey, white, yellow, or brown. It is more likely to stain than marble. Limestone is known to contain lime from sea water.
  • SANDSTONE: Is a very durable formation of quartz grains (sand). Usually formed in light brown or red colors. Categorized by the most popular sandstone bonding agents such as silica, calcium, clay and iron oxide.
  • SOAPSTONE:  A soft stone made of a variety of talc.  Some are soft enough to be scratched by a fingernail, others are relatively scratch-resistant. It is a dense mineral that wears well and is often resistant to stains. 
  • FOSSILSTONE: Considered a limestone that contains natural fossils such as sea shells and plants.
  • TRAVERTINE: Usually a cream or reddish color. It is formed through the accumulation of calcite from hot springs. It contains lots of holes that were formed from water flowing through the stone. These holes are often filled with synthetic resins or cements. Requires lots of maintenance if the holes are not filled. Classified as a limestone and a marble.

II. METAMORPHIC stone originates from a natural change from one type of stone to another type through the mixture of heat, pressure and minerals. The change may be a development of a crystalline formation, a texture change or a color change.

  • MARBLE: A recrystallized limestone that formed when the limestone softened from heat and pressure and recrystallized into marble where mineral changes occurred. The main consistency is calcium and dolomite. Ranges in many colors and is usually heavily veined and shows lots of grains. Hardness rates from 2.5 to 5 on the MOH Scale. Marble is classified into three categories:
    1. Dolomite: If it has more than 40% magnesium carbonate.
    2. Magnesian: If it has between 5% and 40% magnesium carbonate.
    3. Calcite: If it has less than 5% magnesium carbonate.
  • SLATE: A fine-grained metamorphic stone that formed from clay, sedimentary rock shale and sometimes quartz. Very thin and can break easily. Usually black, grey or green.
  • SERPENTINE: Identified by its marks which look like the skin of a serpent. Most popular colors are green and brown. Hardness rates from 2.5 to 4 on the MOH Scale. Contains serpentine minerals, has lots of magnesium and has an igneous origin. Does not always react well to recrystallization or diamond polishing.

III. IGNEOUS stones are mainly formed through volcanic material such as magma. Underneath the Earth’s surface, liquid magma cooled and solidified. Mineral gases and liquids penetrated into the stone and created new crystalline formations with various colors.

  • GRANITE: Primarily made of Quartz (35%), Feldspar (45%) and Potassium. Usually has darker colors. Contains very little calcite, if any. Provides a heavy crystalline and granular appearance with mineral grains. It is very hard material and easier to maintain than marble. Yet, it is still porous and will stain. There are different types of granite depending on the percentage mix of quartz, mica, and feldspar. Black granite is known as an Anorthosite. It contains very little quartz and feldspar and has a different composition than true granite.

IV. SCHIST.  A schist is a stone that has been exposed to intense pressure and heat and has been transformed  (metamorphized) by the process.  The resulting schist retains the chemical characteristics of the original stone, but is far harder and less porous than it was originally. 

  • PIETRA del CARDOSO:  An Italian schist, quarried in the Carrara region, the source of Carrara marble.   Sometimes called a 'metamorphized sandstone', it's a 100% silicate rock that can't be etched by acids like marble, limestone, some granites and other stones, making it an excellent material for countertops.   

V. MAN-MADE stones are derived of unnatural mixtures such as resin or cement mixed with the addition of stone chips.

  • TERRAZZO: Marble and granite chips embedded in a cement composition.
  • AGGLOMERATE or CONGLOMERATE: Marble chips embedded in a colored resin (plastic) composition.
  • CULTURED or FAUX MARBLE: A mix of resins that are painted or mixed with a paint to look like marble.

Surface Textures:

There are many different types of stone available today, OTM has a nice display of the various options. When stone is ordered, it is fabricated with a particular type of surface. Sometimes we can alter the surface (hone a polished slab, for example) if your preferred finish isn't available.:

Honed:  Provides a flat to low sheen gloss. that is very smooth, but often porous. Honed stone colors are not as vibrant as a polished stone.

Polished:  A glossy surface that is very smooth and not very porous. The reflectivity of polished crystals brings out the brilliant colors and grains of natural stone. The shine is not from a coating, but comes from the natural reflection of the stone’s crystals provided by polishing bricks and polishing powders that are used during fabrication.

Flamed: A rough surface that is developed through intense heat. During fabrication, the stone is heated up and the crystals begin to pop, thus forming a rough surface. This surface is very porous and must be generously treated with impregnators.

Sand Blasted: This surface is the result of a pressurized flow of sand and water that provides a textured surface with a matte gloss.

Sawn: A process performed by using a gang saw.

Bush Hammered: A pounding action that develops a textured surface. The degree of roughness can be selected.

 
         
       
 

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Nuance Stoneworks, Inc.  Seattle, WA  206-669-8547  chris at nuancestoneworks.com