Identification guide · Minerals
How to Identify Astrophyllite
Astrophyllite forms bronze, golden, or reddish-brown bladed to feathery crystals with a metallic to pearly luster arranged in radiating star-shaped sprays. Its streak is pale yellow-brown, and it has one perfect cleavage direction with a hardness around 3, soft enough to gouge easily but not scratch glass. The radiating, almost feather-like habit set against pale feldspar matrix is the key identifying feature, separating it from similarly colored micas or amphiboles, which never form true star-burst clusters.
Astrophyllite identification checklist
| Color | Golden-yellow, Bronze, Copper-red, Brown | Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue. |
|---|---|---|
| Luster | Vitreous to pearly/submetallic sheen | Turn it under a lamp: a true metallic shine reflects like polished metal and stays opaque at thin edges. |
| Transparency | Translucent | Hold a thin edge up to a bright light and note whether light passes through. |
| Mohs hardness | 3–3.5 | A copper coin (Mohs 3.5) scratches it, but a fingernail does not. |
| Streak | Brownish yellow | Drag a corner across unglazed porcelain (the back of a bathroom tile) and check the powder color. |
| Cleavage | Perfect basal {001} (micaceous) | |
| Fracture | Uneven | |
| Specific gravity | 3.3–3.4 | Heavier than it looks (specific gravity about 3.3499999999999996). |
| Crystal system | Triclinic |
Astrophyllite look-alikes and how to tell them apart
Both sit near Mohs 3–3.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Astrophyllite vs Calcite →
Both sit near Mohs 3–3.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Astrophyllite vs Bornite →
Both sit near Mohs 3–3.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Astrophyllite vs Copper →
Both sit near Mohs 3–3.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
Astrophyllite identification FAQ
How can you tell if a rock is Astrophyllite?
Check the color (golden-yellow, bronze, copper-red, and brown), the vitreous to pearly/submetallic sheen luster, a Mohs hardness of 3–3.5 and a brownish yellow streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Astrophyllite?
Astrophyllite has a Mohs hardness of 3–3.5. A copper coin (Mohs 3.5) scratches it, but a fingernail does not.
What is the difference between Astrophyllite and Calcite?
Astrophyllite (Mohs 3–3.5, vitreous to pearly/submetallic sheen luster) and Calcite (Mohs 3, vitreous luster) look alike, but hardness, streak and heft usually separate them. See the full Astrophyllite vs Calcite comparison for a side-by-side table.
Is Astrophyllite worth anything?
Entry-level Astrophyllite 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 Astrophyllite?
Astrophyllite is most often golden-yellow, bronze, copper-red, and brown. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
