Ever Wondered If Your Crystal is Fake ?

D'Crystals
3 days ago
2 min read

Crystals come in all colors and forms—but how can you truly tell them apart? Beyond visual inspection, gemologists and collectors use three reliable scientific methods: Mohs Hardness, Specific Gravity, and Refractive Index. Let’s break down how each method works—and explore a full table of popular crystals based on these characteristics.

Mohs Hardness Scale – How Tough Is Your Crystal?

The Mohs scale measures how resistant a crystal is to scratching, ranking minerals from 1 (very soft) to 10 (very hard). The higher the number, the harder the mineral.

Crystal	Mohs Hardness
Diamond	10
Topaz	8
Quartz, Amethyst, Citrine	7
Garnet	6.5 – 7.5
Peridot	6.5 – 7
Moonstone	6 – 6.5
Amazonite	6 – 6.5
Labradorite	6 – 6.5
Rhodonite	5.5 – 6.5
Turquoise	5 – 6
Fluorite	4
Amber	2 – 2.5

Specific Gravity – Weight Without the Bulk

Specific Gravity (SG) is the ratio of a crystal's density compared to water. Denser stones feel heavier for their size.

Crystal	Specific Gravity
Diamond	3.52
Topaz	3.49 – 3.57
Garnet	3.5 – 4.3
Rhodonite	3.4 – 3.7
Fluorite	3.18
Peridot	3.2 – 4.3
Labradorite	2.68 – 2.72
Quartz (incl. Amethyst, Citrine)	2.65
Sunstone	2.62 – 2.65
Amazonite	2.56 – 2.58
Moonstone	2.56 – 2.60
Aquamarine	2.68 – 2.74
Morganite	2.71 – 2.90
Turquoise	2.6 – 2.9
Amber	1.05 – 1.10

Refractive Index – The Light Test

Refractive Index (RI) measures how much light bends as it passes through a crystal. Each crystal has a unique RI range.

Crystal	Refractive Index (RI)
Diamond	2.42
Zircon	1.81 – 2.02
Garnet	1.73 – 1.89
Rhodonite	1.716 – 1.753
Topaz	1.609 – 1.643
Peridot	1.65 – 1.69
Aquamarine	1.577 – 1.583
Quartz (incl. Amethyst, Citrine)	1.544 – 1.553
Sunstone	1.525 – 1.552
Amazonite	1.522 – 1.530
Moonstone	1.518 – 1.526
Labradorite	1.559 – 1.573
Turquoise	1.61 – 1.65
Fluorite	1.433 – 1.436
Amber	1.54

Why You Should Use All Three Together

Relying on just one test can be misleading. For example:

Quartz vs. Glass: Look similar, but quartz has a higher hardness and distinct RI.
Citrine vs. Topaz: Both yellow, but topaz is harder and denser.

Using Mohs + SG + RI gives you near-certain identification, especially when crystals are polished or tumbled.

Did You Know?

Colored glass often mimics crystals—but fails hardness and SG tests.
Fake turquoise usually has a much lower SG and inconsistent RI.
Diamond testers combine RI and conductivity for accuracy.

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