RocksdayAlmandine vs Ruby
The quickest way to tell Almandine from Ruby: Ruby is clearly harder: Mohs 9 versus 7–7.5.
The common iron garnet: dark red to purplish, and heavy. It is the garnet in most mica schists.
Photo: Didier Descouens, CC BY-SA 4.0
Red corundum, colored by chromium. After diamond it's the hardest natural gemstone.
Photo: Robert M. Lavinsky, CC BY-SA 3.0
Quick tests
- Hardness: Ruby is clearly harder: Mohs 9 versus 7–7.5.
Key differences
- Ruby is harder and grows in hexagonal barrels.
Side by side
| Property | Almandine | Ruby |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 7–7.5 | 9 |
| Luster | Vitreous | Adamantine to vitreous |
| Streak | White | White |
| Colors | Red, Purple, Brown | Red, Pink |
| Crystal system | Cubic | Trigonal |
| Specific gravity | 4–4.3 | 3.97–4.05 |
| Formula | Fe₃Al₂(SiO₄)₃ | Al₂O₃ (with chromium) |
| Found in | Gore Mountain, New York; Tyrol, Austria | Mogok, Myanmar; Montepuez, Mozambique |
Properties that are the same for both are grayed out.
How to identify almandine
- Dark red or purplish rounded crystals, often in schist.
- Hardness 7–7.5.
- Noticeably heavy for its size.
Crystal system: Cubic
Full Almandine guide →How to identify ruby
- Red to pinkish red, often in six-sided barrel crystals.
- Hardness 9 — scratches topaz and quartz.
- Glows red under a UV light.
Crystal system: Trigonal
Full Ruby guide →More comparisons
Frequently asked questions
What is the difference between almandine and ruby?
Almandine is a mineral with a Mohs hardness of 7–7.5 and a vitreous luster, usually red, purple or brown. Ruby is a mineral with a Mohs hardness of 9 and an adamantine to vitreous luster, usually red or pink.
How can you tell almandine from ruby?
Ruby is clearly harder: Mohs 9 versus 7–7.5. Ruby is harder and grows in hexagonal barrels.
Could you tell them apart from a blurry close-up?
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