Identification guide · Minerals
How to Identify Diaspore
Diaspore ranges from colorless and white to gray, yellowish, or greenish, with a vitreous to pearly luster on cleavage surfaces and a white streak. It is notably hard for an aluminum hydroxide mineral, around 6.5 to 7 on the Mohs scale, with perfect cleavage in one direction and a splintery fracture. A useful diagnostic is its tendency to decrepitate, splitting apart with an audible crackle, when heated in a flame. It can be confused with corundum, topaz, or boehmite, though its lower hardness rules out corundum.
Diaspore identification checklist
| Color | Colorless, White, Gray, Yellowish, Brown, Green, Violet-pink (color-change) | Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue. |
|---|---|---|
| Luster | Vitreous to pearly on cleavage | Fresh surfaces shine like glass; a dull surface usually means weathering, so chip or wet a corner. |
| Transparency | Transparent to translucent | Hold a thin edge up to a bright light and note whether light passes through. |
| Mohs hardness | 6.5–7 | It scratches glass and a steel knife and cannot be scratched by a steel file. |
| Streak | White | Drag a corner across unglazed porcelain (the back of a bathroom tile) and check the powder color. |
| Cleavage | Perfect on {010} | |
| Fracture | Conchoidal | Broken surfaces show smooth, curved, shell-like scoops. |
| Specific gravity | 3.3–3.5 | Heavier than it looks (specific gravity about 3.4). |
| Crystal system | Orthorhombic |
Extra tests for Diaspore
Glass check. Diaspore shares a glassy luster and conchoidal fracture with man-made glass. Glass sits near Mohs 5.5 and often contains round gas bubbles, so a hardness test and a hand lens separate them.
Diaspore look-alikes and how to tell them apart
Both sit near Mohs 6.5–7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Diaspore vs Feldspar →
Both sit near Mohs 6.5–7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Diaspore vs Quartz →
Diaspore is harder (Mohs 6.5–7) than Calcite (Mohs 3), so Diaspore will scratch Calcite and not the other way round. A copper coin (Mohs 3.5) scratches it, but a fingernail does not. Diaspore vs Calcite →
Both sit near Mohs 6.5–7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
Diaspore identification FAQ
How can you tell if a rock is Diaspore?
Check the color (colorless, white, gray, and yellowish), the vitreous to pearly on cleavage luster, a Mohs hardness of 6.5–7 and a white streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Diaspore?
Diaspore has a Mohs hardness of 6.5–7. It scratches glass and a steel knife and cannot be scratched by a steel file.
What is the difference between Diaspore and Feldspar?
Diaspore (Mohs 6.5–7, vitreous to pearly on cleavage luster) and Feldspar (Mohs 6–6.5, vitreous to pearly luster) look alike, but hardness, streak and heft usually separate them. See the full Diaspore vs Feldspar comparison for a side-by-side table.
Is Diaspore worth anything?
Entry-level Diaspore specimens sell for around $2, typical collector pieces about $20, and premium examples $150 or more depending on size, quality and locality.
What color is Diaspore?
Diaspore is most often colorless, white, gray, and yellowish. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
