Comparison · Semi-Precious Stones vs Silicate Minerals
Garnet vs Sillimanite
Garnet and Sillimanite are easy to confuse. Both sit near Mohs 7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Garnet and Sillimanite
- Both sit near Mohs 7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Garnet feels noticeably heavier for its size (specific gravity 3.8 versus 3.24 for Sillimanite).
- They overlap in green and brown, but Garnet also comes in red, orange, and purple and Sillimanite also comes in white, gray, and yellow.
- Well-formed crystals give it away: Garnet is cubic, Sillimanite is orthorhombic.
Garnet vs Sillimanite properties
| Property | Garnet | Sillimanite |
|---|---|---|
| Type | Semi-Precious Stones | Silicate Minerals |
| Mohs hardness | 7 | 7 |
| Luster | vitreous | vitreous |
| Streak | White | White |
| Transparency | transparent | transparent |
| Specific gravity | 3.8 | 3.24 |
| Crystal system | cubic | orthorhombic |
| Common colors | Red, Orange, Green, Purple, Brown | White, Gray, Brown, Pale green, Yellow |
| Rarity | common | uncommon |
| Typical specimen value | $10–$3000+ | $10–$450+ |
Which is more valuable?
Garnet is usually the more valuable of the two: a typical collector specimen runs about $100 against $70 for Sillimanite, and premium Garnet can reach $3000 or more.
About Garnet
Garnet is a group of silicate minerals that share similar crystal structures. While red garnets are most common, they occur in every color except blue.
About Sillimanite
Sillimanite is an aluminum silicate mineral that forms slender prismatic crystals or fibrous masses, the fibrous variety being called fibrolite. It is one of three aluminosilicate minerals that share the same composition but differ in structure.
Garnet vs Sillimanite FAQ
Is Garnet the same as Sillimanite?
No. Garnet is a semi-precious stone while Sillimanite is a silicate mineral. Both sit near Mohs 7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Garnet from Sillimanite?
Both sit near Mohs 7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Garnet feels noticeably heavier for its size (specific gravity 3.8 versus 3.24 for Sillimanite). They overlap in green and brown, but Garnet also comes in red, orange, and purple and Sillimanite also comes in white, gray, and yellow.
Which is harder, Garnet or Sillimanite?
They are about equally hard, both near Mohs 7.
Which is more valuable, Garnet or Sillimanite?
Garnet is usually the more valuable of the two: a typical collector specimen runs about $100 against $70 for Sillimanite, and premium Garnet can reach $3000 or more.
