Comparison · Semi-Precious Stones
Moonstone vs Opal
Moonstone and Opal are easy to confuse because both are semi-precious stones. Both sit near Mohs 6, 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 Moonstone and Opal
- Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Moonstone feels noticeably heavier for its size (specific gravity 2.6 versus 2.1 for Opal).
- They overlap in white, pink, and blue, but Moonstone also comes in gray and Opal also comes in black.
- Well-formed crystals give it away: Moonstone is monoclinic, Opal is amorphous.
Moonstone vs Opal properties
| Property | Moonstone | Opal |
|---|---|---|
| Type | Semi-Precious Stones | Semi-Precious Stones |
| Mohs hardness | 6 | 5.5 |
| Luster | vitreous | vitreous |
| Streak | White | White |
| Transparency | translucent | translucent |
| Specific gravity | 2.6 | 2.1 |
| Crystal system | monoclinic | amorphous |
| Common colors | White, Gray, Peach, Blue sheen | White, Black, Fire, Blue, Pink |
| Rarity | uncommon | 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 $50 for Moonstone, and premium Opal can reach $10000 or more.
About Moonstone
Moonstone is a feldspar mineral known for its adularescence—a billowy blue-white light that moves across the surface like moonlight on water.
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.
Moonstone vs Opal FAQ
Is Moonstone the same as Opal?
No. Both are semi-precious stones, but they are distinct species with different hardness, streak or luster. Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Moonstone from Opal?
Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Moonstone feels noticeably heavier for its size (specific gravity 2.6 versus 2.1 for Opal). They overlap in white, pink, and blue, but Moonstone also comes in gray and Opal also comes in black.
Which is harder, Moonstone or Opal?
Moonstone is harder: Mohs 6 against Mohs 5.5 for Opal.
Which is more valuable, Moonstone or Opal?
Opal is usually the more valuable of the two: a typical collector specimen runs about $500 against $50 for Moonstone, and premium Opal can reach $10000 or more.
