Identification guide · Minerals
How to Identify Diopside
Diopside ranges from colorless and pale green to deep chrome-green or brown, with a vitreous luster and a white to pale green streak. It has a hardness of 5.5 to 6.5 and two cleavage directions meeting at nearly ninety degrees, a signature trait of the pyroxene group that distinguishes it from amphiboles, whose cleavage meets at about 56 and 124 degrees. Diopside is commonly confused with augite and hornblende, but its lighter color, pyroxene-angle cleavage, and typical occurrence in marble or basalt help separate it from these related minerals.
Diopside identification checklist
| Color | Light to dark green, White, Gray, Blue-violet (violane), Black (chromian varieties) | Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue. |
|---|---|---|
| Luster | Vitreous | 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 | 5.5–6.5 | It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will. |
| Streak | White | Drag a corner across unglazed porcelain (the back of a bathroom tile) and check the powder color. |
| Cleavage | Good prismatic (~87°/93°) | |
| Fracture | Conchoidal to uneven | Broken surfaces show smooth, curved, shell-like scoops. |
| Specific gravity | 3.2–3.3 | Heavier than it looks (specific gravity about 3.25). |
| Crystal system | Monoclinic |
Extra tests for Diopside
Glass check. Diopside 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.
Diopside look-alikes and how to tell them apart
Both sit near Mohs 5.5–6.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Diopside vs Aegirine →
Both sit near Mohs 5.5–6.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Diopside vs Augite →
Quartz is harder (Mohs 7) than Diopside (Mohs 5.5–6.5), so Quartz will scratch Diopside 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. Diopside vs Quartz →
Both sit near Mohs 5.5–6.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Diopside vs Spodumene →
Diopside identification FAQ
How can you tell if a rock is Diopside?
Check the color (light to dark green, white, gray, and blue-violet (violane)), the vitreous luster, a Mohs hardness of 5.5–6.5 and a white streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Diopside?
Diopside has a Mohs hardness of 5.5–6.5. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will.
What is the difference between Diopside and Aegirine?
Diopside (Mohs 5.5–6.5, vitreous luster) and Aegirine (Mohs 6–6.5, vitreous luster) look alike, but hardness, streak and heft usually separate them. See the full Diopside vs Aegirine comparison for a side-by-side table.
Is Diopside worth anything?
Entry-level Diopside 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 Diopside?
Diopside is most often light to dark green, white, gray, and blue-violet (violane). Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
