Hardness of Stone

A scale for the hardness of minerals is first published in 1822 by Frederick Mohs, an Austriam mineralogist who formulated a scale by using a srcatc -test that was used in mines.

The scale runs from 1 upto 10 and is not proportional

The relative difference between scale 5 and 3 is smaller then the difference between scale 1 and 2! There is no need to be worried about working in stone with harness 5,you might hardly notice the difference with hardness 3.
The step from 5 to 6 is well noticeable, as is the step from 6 to 7.
From 7 to 8 the difference is again relatively small and from 8 to 9 very obvious.
The final stop from 9 to 10 is relatively the largest step. Now you are working in diamant.!

Below you can find an overview of the minerals that determine the hardness, and the stones suitable for sculpturing that fall within that scale. This does not mean that the stone is composed of the hardness-determining mineral .
Most stones are present in different hardness-scales. This is since most stones are composed by several minerals.

Talc
Gypsum
Calcite (calcspar)
Fluorite (fluorspar)
calcium phosphate / Apatite (Fluorapatite)
Orthoclase
Quartz
Topaz
Corundum
Diamond

Scratch-test
The scratch test makes it fairly easy to test a stone for its hardness.

A stone with hardness 1 leaves a mark on paper
With your fingernail you can scratch minerals upto a hardness of 2.5
With a coper coin you can scratch minerals upto a hardness of 3.5
With glass or a nail you can scratch minerals upto a hardness of 5.5
As from hardness 5.5. a stone scratches glass

The right tools

Tools for stones with a hardness upto 2 Soapstone chisels and rasps This categorie is suitable for beginners and amateurs
Tools for stones with a hardness upto 4.5 Steel tools, like Miliani rasps and chisels It is wise to do a course before working with these materials to avoid damage or wear out due to misuse.
Tools for stones with a hardness upto 6.5 Carbide granulated rasps and widia tipped tools, pneumatic and manual tools from Rebit A thorough course with a sculpturer is required. Misuse of widia tipped tools is disastrous for the material. In case of pneumatic application a thorough course is essential to prevent wear down of material, avoidable breaking of the stone and risk of personal injury!
Tools for stones with a hardness upto 8 Diamond rasps and Rebit tools Pneumatic application is required, a thorough course is essential to prevent wear down of material, avoidable breaking of the stone and risk of personal injury!

Alabaster

White opaque

Marble, limestone, granite

Serpentine

Soapstone Asia

Soapstone Brazil

ArtistiX & Service

Visit our Central Warehouse

ArtistiX BV
Nijverheidsweg 19
6651 KS Druten
+31 104654528

Monday till Friday 9-12h and 13-17h.
We regularly have new stones arriving from all over the world. Besides a cup of Coffee you have the benefit of first choice!

If you are not a customer of ArtistiX yet, then please contact us before visiting.

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