Identification guide · Minerals
How to Identify Aegirine
Look for slender, elongated prismatic crystals with a nearly square cross-section, often striated lengthwise and terminated in a wedge. Color ranges from dark green through brown to nearly black, with a vitreous luster and a pale green to grayish streak. Hardness of about 6 separates it from softer amphiboles like hornblende, which shares a similar habit but has different cleavage angles; aegirine's two cleavage planes meet near 87 and 93 degrees, the classic pyroxene angle.
Aegirine identification checklist
| Color | Dark green, Black, Brown-green | 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 | Translucent to opaque | Hold a thin edge up to a bright light and note whether light passes through. |
| Mohs hardness | 6–6.5 | It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will. |
| Streak | Pale green to grayish yellow | Drag a corner across unglazed porcelain (the back of a bathroom tile) and check the powder color. |
| Cleavage | Good prismatic, two directions at ~87°/93° | |
| Fracture | Uneven to splintery | |
| Specific gravity | 3.4–3.6 | Heavier than it looks (specific gravity about 3.5). |
| Crystal system | Monoclinic |
Aegirine look-alikes and how to tell them apart
Both sit near Mohs 6–6.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Aegirine vs Augite →
Both sit near Mohs 6–6.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Aegirine vs Diopside →
Both sit near Mohs 6–6.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Aegirine vs Hornblende →
Both sit near Mohs 6–6.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
Aegirine identification FAQ
How can you tell if a rock is Aegirine?
Check the color (dark green, black, and brown-green), the vitreous luster, a Mohs hardness of 6–6.5 and a pale green to grayish yellow streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Aegirine?
Aegirine has a Mohs hardness of 6–6.5. 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 Aegirine and Augite?
Aegirine (Mohs 6–6.5, vitreous luster) and Augite (Mohs 5.5–6, vitreous to resinous luster) look alike, but hardness, streak and heft usually separate them. See the full Aegirine vs Augite comparison for a side-by-side table.
Is Aegirine worth anything?
Entry-level Aegirine 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 Aegirine?
Aegirine is most often dark green, black, and brown-green. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
