Comparison · Gemstones vs Semi-Precious Stones
Ammolite vs Opal
Ammolite and Opal are easy to confuse. Ammolite is harder (Mohs 7) than Opal (Mohs 5.5), so Ammolite will scratch Opal and not the other way round. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Ammolite and Opal
- Ammolite is harder (Mohs 7) than Opal (Mohs 5.5), so Ammolite will scratch Opal and not the other way round. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will.
- Streak color differs: Ammolite leaves a white to light-colored streak on unglazed porcelain, Opal leaves white.
- Ammolite feels noticeably heavier for its size (specific gravity 3 versus 2.1 for Opal).
Ammolite vs Opal properties
| Property | Ammolite | Opal |
|---|---|---|
| Type | Gemstones | Semi-Precious Stones |
| Mohs hardness | 7 | 5.5 |
| Luster | vitreous | vitreous |
| Streak | White to light-colored | White |
| Transparency | translucent | translucent |
| Specific gravity | 3 | 2.1 |
| Crystal system | varies | amorphous |
| Common colors | Various | White, Black, Fire, Blue, Pink |
| Rarity | common | uncommon |
| Typical specimen value | $10–$500+ | $50–$10000+ |
Which is more valuable?
Opal is usually the more valuable of the two: a typical collector specimen runs about $500 against $75 for Ammolite, and premium Opal can reach $10000 or more.
About Ammolite
Ammolite is organic gemstone formed when it mixes with fossilized shell of extinct marine ammonite.
About Opal
Opal is famous for its play-of-color, caused by the diffraction of light through microscopic silica spheres. Australia produces 95% of the world's opals.
Ammolite vs Opal FAQ
Is Ammolite the same as Opal?
No. Ammolite is a gemstone while Opal is a semi-precious stone. Ammolite is harder (Mohs 7) than Opal (Mohs 5.5), so Ammolite will scratch Opal and not the other way round. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will.
How can you tell Ammolite from Opal?
Ammolite is harder (Mohs 7) than Opal (Mohs 5.5), so Ammolite will scratch Opal and not the other way round. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will. Streak color differs: Ammolite leaves a white to light-colored streak on unglazed porcelain, Opal leaves white. Ammolite feels noticeably heavier for its size (specific gravity 3 versus 2.1 for Opal).
Which is harder, Ammolite or Opal?
Ammolite is harder: Mohs 7 against Mohs 5.5 for Opal.
Which is more valuable, Ammolite or Opal?
Opal is usually the more valuable of the two: a typical collector specimen runs about $500 against $75 for Ammolite, and premium Opal can reach $10000 or more.
