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.