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Identity Helphardness test: 7 scratches Quartz?

11th Jun 2017 16:04 UTCSophiaJoy MB

I’ve been doing a hardness test on Amethyst on a ring because the seller says it’s a natural Amethyst but I was not sure and thought it could be CZ.

I used a hardness test tool, and found that the hardness 7 didn’t scratch the stone first, but I kept trying and eventually the tool scratched it.

Can the hardness 7 scratch Quartz…sometimes??

CZ is 8 to 8.5, right?

In this situation, is there anything else I can try to find out if the stone is natural Amethyst?

(I also used a lupe but couldn't find any inclusions)

Thanks!

11th Jun 2017 19:42 UTCVolkmar Stingl

CZ?

11th Jun 2017 20:57 UTCErik Vercammen Expert

I suppose it is the abbreviation of Cubic Zirconia, a classic manmade "gemstone"

11th Jun 2017 21:06 UTCWayne Corwin

Sophiajoy

were all your 'trys' in the exact same spot, over & over in the same line?

12th Jun 2017 01:07 UTCSophiaJoy MB

Yes, CZ is Cubic Zirconia.

Wayne,

Yes, I tried the exact same spot, over and over. I tried two lines, and the tool (hardness 7) scratched both.

12th Jun 2017 03:08 UTCDonald B Peck Expert

Sophia, part of the testing protocol for Mohs Hardness is to test scratch both ways. Does the mineral with known hardness scratch the mineral with unknown hardness, and vice-versa. I know you cannot do this when you use the hardness points, but with known minerals each will scratch the other when the hardnesses are equal; BUT with great difficulty. You, I think, experienced the difficulty.

I recommend collecting samples of each of the first nine minerals in the Mohs series to build a hardness kit. Cleavage blocks work well when they are possible, when they are not a crystal with flat faces and points will work.

sophia

12th Jun 2017 05:39 UTCJoel Dyer

Hi Sophiajoy,

If you deal with quite smooth and flat surfaces from time to time, a refractometer is one of the best ways to differentiate between a large amount of minerals / gemstones. This includes many cabachon stones and natural crystals.

Quartz has much lower refractive indices compared to CZ, which is "over the limit" of traditional refractometers (but not reflectometers). A self-made polariscope also helps to differentitate between isometric and anisotropic minerals / gemstones.

As for differentiating between very clean natural and synthetic amethyst, that's a bit more advanced a subject & I wouldn't want to swear on an origin myself, if the signs are not very clear. Synthetical and also treatment processes have advanced extremely far in the last decades.

Cheers,

Joel

13th Jun 2017 10:20 UTCSophiaJoy MB

Thank you very much!!

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