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STONE HARDNESS - THE MOHs SCALE

 

                                                   
  STONE TYPES FOR CARVING
10  Diamond  Hardest material known
     
 9  Ruby, Corundum  Harder than Topaz
Verdite
     
 8  Topaz
 Harder the quartz
Verdite
 Springstone
   
 7  Quartz
 Scratches glass
Verdite
 Springstone  Butter-jade
 
 6  Microline/Feldspar  Suitable for gems
 
 Leopard stone
 Butter-jade  Africa stone
 5  Apatite  About the hardness of teeth
Serpentine  Cobalt
 Opalstone  Africa stone
 4  Flourite
 Cannot be scratched with nail
Serpentine
   

 Africa stone

 3  Calcite
 Difficult to scratch with a nail
Soapstone
     
 2  Gypsum
 Easily scratched with a nail
Soapstone      
 1  Talc
 Very soft, chalk-like
       

Notes:

The hardness scale above is an indication of the quality of material.

Fingernails: 2.5 * Copper coin: 3.5 * Knife-glass: 5.5 * Tool steel: 6.5 *

Soapstone is also described as "rapocco" but is still a very soft stone. When you rub your fingers on the base, then your fingers will have a soapy feeling when you rub them together. The low grades of soapstone will deteriorate in ordinary air and can decay because of the air reaction on the stone. Generally soapstone can easily "bruise", and cannot be polished successfully. Test the material by scratching the bottom with fingernail, if it marks very easily then it will be soapstone. At BATANAI we rarely sell soapstone because the articles are very often too fragile to last.

All stones will have inclusions of various minerals that enhance the colours. Some have inclusions or strips of corundum or other hard minerals, which may appear to be a flaw but in reality is not.

Some rare examples of Verdite are exceptionally clean and green, whilst others (more common) have heavy brown colouring.

It takes a trained person who has an extensive knowledge of minerals to identify the stone and detect potential or real flaws. At BATANAI our staff have this training, and our artwork is based on this knowledge and experience.