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Good Price Mohs Hardness Pen FMH-10 Complete Kit with Pen for All Hardnesses 1-10 Very Important Tool in Being able to Verify Gemstones A Must for Collectors and Professionals Buy Now!

Using hardness pens is a quick and classic method for rough grading and identifying gemstones. It is based on the Mohs hardness scale, which tests a stone's ability to scratch or be scratched by reference material. Since each mineral has a specific hardness, this is a very useful exclusion tool. A hardness pen is used to scratch raw gemstones. If there are scratches, the gemstone's hardness is lower than the hardness indicated on the pen.

Mohs hardness from 1 to 10. It includes:

1, Talc
2, Gypsum
3, Calcite
4, Fluorite
5, Apatite
6, Feldspar
7, Quartz
8, Topaz
9, Corundum
10, Diamond

Here is a quick guide to how the pens work:

Mohs hardness scale (reference material)

The scale ranges from 1 to 10, with 1 being the softest and 10 being the hardest (diamond). The hardness pens have tips made of different materials that correspond to the steps on the scale:

1–3: Talc, gypsum, calcite
4–5: Fluorite, apatite
6–7: Feldspar, quartz
8–10: Topaz, corundum (sapphire/ruby), diamond

How the test is done

• You choose a hardness on the pen and make a very careful, small scratch on a hidden part of the gemstone (for example, the underside or edge of the stone).
• If the stone is scratched: The stone is softer than the tip of the pen.
• If the stone is NOT scratched: The stone is as hard or harder than the tip of the pen.

Benefits and uses

• Fast and direct indication: Provides immediate answers in the field.
• Distinguishes fakes from genuine: Perfect for, for example, distinguishing genuine harder stones (such as sapphire with a hardness of 9) from softer imitations (such as glass with a hardness of 5-6).

Important limitations and risks

• Risk of damage: The method is destructive because it causes a permanent (albeit often small) scratch. This can destroy the value of cut and faceted collector stones.
• Brittle stones: A hard stone can be brittle and risk cracking if you press too hard.
• Crystal direction: Some stones have different hardnesses depending on which crystal axis you are testing (e.g. kyanite which varies between 4 and 7).
• Safety margin: You should always start with a pencil with a lower hardness than you suspect the stone has to avoid damaging it unnecessarily.