SET OF 5 MOHS SCALE HARDNESS PENCILS
This set of 5 hardness pencils covers the range of Moh's Scales from 5 through to 9.
Hardness pencils are pencils with a tip made of one of the minerals on Mohs scale. These pencils are used to try and scratch a stone and observe if the pencils can scratch the gem.
Since this is a destructive method (it leaves a scratch), this test is mostly used on pieces of rough or on a inconspicuous place on the gemstone.
The gemstone is tested with a pencil of low hardness (starting at 4 or lower) to try to put a tiny scratch on the stone without applying pressure. If no scratch is observed, one repeats this process with a pencil of higher hardness (in this case 5) and so on until one arrives at the pencil that is able to put a tiny scratch on the stone.
For instance, if one could not scratch the mineral with pencil no.7 but it would leave a scratch with pencil no.8, the hardness of the mineral must be between 7 and 8 on Mohs scale.
Be The First To Review This Product!
Help other Gemcuts users shop smarter by writing reviews for products you have purchased.