Comparison · Semi-Precious Stones vs Precious Stones
Iolite vs Sapphire
Iolite and Sapphire are easy to confuse. Sapphire is harder (Mohs 9) than Iolite (Mohs 7), so Sapphire will scratch Iolite and not the other way round. It scratches glass and a steel knife and cannot be scratched by a steel file. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Iolite and Sapphire
- Sapphire is harder (Mohs 9) than Iolite (Mohs 7), so Sapphire will scratch Iolite and not the other way round. It scratches glass and a steel knife and cannot be scratched by a steel file.
- Sapphire feels noticeably heavier for its size (specific gravity 4 versus 2.6 for Iolite).
- They overlap in blue, but Iolite also comes in purple and gray and Sapphire also comes in pink, yellow, orange, green, and white.
- Well-formed crystals give it away: Iolite is orthorhombic, Sapphire is trigonal.
Iolite vs Sapphire properties
| Property | Iolite | Sapphire |
|---|---|---|
| Type | Semi-Precious Stones | Precious Stones |
| Mohs hardness | 7 | 9 |
| Luster | vitreous | adamantine |
| Streak | White | White |
| Transparency | transparent | transparent |
| Specific gravity | 2.6 | 4 |
| Crystal system | orthorhombic | trigonal |
| Common colors | Violet-Blue, Blue, Gray | Blue, Pink, Yellow, Orange, Green, White |
| Rarity | uncommon | rare |
| Typical specimen value | $30–$800+ | $500–$50000+ |
Which is more valuable?
Sapphire is usually the more valuable of the two: a typical collector specimen runs about $5000 against $100 for Iolite, and premium Sapphire can reach $50000 or more.
About Iolite
Iolite is the gem variety of cordierite, showing strong pleochroism—appearing different colors from different angles. Vikings may have used it for navigation.
About Sapphire
Sapphire is a variety of corundum in any color except red. Blue sapphires are most prized, especially the legendary Kashmir stones.
Iolite vs Sapphire FAQ
Is Iolite the same as Sapphire?
No. Iolite is a semi-precious stone while Sapphire is a precious stone. Sapphire is harder (Mohs 9) than Iolite (Mohs 7), so Sapphire will scratch Iolite and not the other way round. It scratches glass and a steel knife and cannot be scratched by a steel file.
How can you tell Iolite from Sapphire?
Sapphire is harder (Mohs 9) than Iolite (Mohs 7), so Sapphire will scratch Iolite and not the other way round. It scratches glass and a steel knife and cannot be scratched by a steel file. Sapphire feels noticeably heavier for its size (specific gravity 4 versus 2.6 for Iolite). They overlap in blue, but Iolite also comes in purple and gray and Sapphire also comes in pink, yellow, orange, green, and white.
Which is harder, Iolite or Sapphire?
Sapphire is harder: Mohs 9 against Mohs 7 for Iolite.
Which is more valuable, Iolite or Sapphire?
Sapphire is usually the more valuable of the two: a typical collector specimen runs about $5000 against $100 for Iolite, and premium Sapphire can reach $50000 or more.
