Comparison · Minerals
Cordierite vs Diaspore
Cordierite and Diaspore are easy to confuse because both are minerals. Both sit near Mohs 7–7.5, 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 Cordierite and Diaspore
- Both sit near Mohs 7–7.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Diaspore feels noticeably heavier for its size (specific gravity 3.3–3.5 versus 2.6–2.66 for Cordierite).
- They overlap in purple, gray, and yellow, but Cordierite also comes in blue and Diaspore also comes in clear, brown, green, and pink.
Cordierite vs Diaspore properties
| Property | Cordierite | Diaspore |
|---|---|---|
| Type | Minerals | Minerals |
| Mohs hardness | 7–7.5 | 6.5–7 |
| Luster | Vitreous | Vitreous to pearly on cleavage |
| Streak | White | White |
| Transparency | Transparent to translucent | Transparent to translucent |
| Specific gravity | 2.6–2.66 | 3.3–3.5 |
| Crystal system | Orthorhombic | Orthorhombic |
| Common colors | Blue, Violet-blue, Gray, Yellowish gray | Colorless, White, Gray, Yellowish, Brown, Green, Violet-pink (color-change) |
| Rarity | common | common |
| Typical specimen value | $2–$150+ | $2–$150+ |
Which is more valuable?
Typical specimens of Cordierite and Diaspore trade in a similar range, around $20.
About Cordierite
Cordierite is a magnesium iron aluminum cyclosilicate, (Mg,Fe)2Al4Si5O18, best known for its strong pleochroism, appearing blue-violet, gray, or pale yellow depending on the angle from which it is viewed. Its transparent gem variety, called iolite, has long been nicknamed 'water sapphire' for its violet-blue color. It crystallizes in the orthorhombic system and typically forms stubby, pseudo-hexagonal crystals.
About Diaspore
Diaspore is aluminum oxide hydroxide, AlO(OH), a hard, dense mineral that forms in aluminum-rich metamorphic and hydrothermal environments and ranks among the principal minerals in bauxite ore. It is dimorphous with boehmite, sharing an identical chemical formula but a different crystal structure, and it characteristically splits apart with a sudden crackling sound when heated, a property that inspired its name. Transparent gem-quality crystals, sold as zultanite or csarite, display a striking color change from green to pink or champagne under different lighting.
Cordierite vs Diaspore FAQ
Is Cordierite the same as Diaspore?
No. Both are minerals, but they are distinct species with different hardness, streak or luster. Both sit near Mohs 7–7.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Cordierite from Diaspore?
Both sit near Mohs 7–7.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Diaspore feels noticeably heavier for its size (specific gravity 3.3–3.5 versus 2.6–2.66 for Cordierite). They overlap in purple, gray, and yellow, but Cordierite also comes in blue and Diaspore also comes in clear, brown, green, and pink.
Which is harder, Cordierite or Diaspore?
Cordierite is harder: Mohs 7–7.5 against Mohs 6.5–7 for Diaspore.
Which is more valuable, Cordierite or Diaspore?
Typical specimens of Cordierite and Diaspore trade in a similar range, around $20.
