Identification guide · Minerals
How to Identify Satin Spar
Satin Spar is usually white, cream, and colorless with a silky luster and is translucent. It has a Mohs hardness of 2. A fingernail (Mohs 2.5) scratches it easily. Its streak is white. It is most often confused with Selenite, Anhydrite, and Gypsum; the tests below separate them.
Satin Spar identification checklist
| Color | White, Cream, Colorless, Peach | Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue. |
|---|---|---|
| Luster | Silky | Compare a fresh surface with glass and metal; this luster is softer than either. |
| Transparency | Translucent | Hold a thin edge up to a bright light and note whether light passes through. |
| Mohs hardness | 2 | A fingernail (Mohs 2.5) scratches it easily. |
| Streak | White | Drag a corner across unglazed porcelain (the back of a bathroom tile) and check the powder color. |
| Cleavage | Perfect | |
| Fracture | Fibrous | |
| Specific gravity | 2.3 | Ordinary rock-like heft (specific gravity about 2.3), similar to quartz. |
| Crystal system | Monoclinic |
Satin Spar look-alikes and how to tell them apart
Both sit near Mohs 2, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Satin Spar vs Selenite →
Anhydrite is harder (Mohs 3–3.5) than Satin Spar (Mohs 2), so Anhydrite will scratch Satin Spar and not the other way round. A fingernail (Mohs 2.5) scratches it easily. Satin Spar vs Anhydrite →
Both sit near Mohs 2, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Satin Spar vs Gypsum →
Both sit near Mohs 2, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
Field tips
- Look for silky fibrous bands and white to cream translucency.
- Confirm softness; gypsum scratches easily with a fingernail.
- Do not confuse fibrous satin spar with clear platy selenite crystals.
Satin Spar identification FAQ
How can you tell if a rock is Satin Spar?
Check the color (white, cream, colorless, and peach), the silky luster, a Mohs hardness of 2 and a white streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Satin Spar?
Satin Spar has a Mohs hardness of 2. A fingernail (Mohs 2.5) scratches it easily.
What is the difference between Satin Spar and Selenite?
Satin Spar (Mohs 2, silky luster) and Selenite (Mohs 2, vitreous luster) look alike, but hardness, streak and heft usually separate them. See the full Satin Spar vs Selenite comparison for a side-by-side table.
Is Satin Spar worth anything?
Entry-level Satin Spar specimens sell for around $5, typical collector pieces about $20, and premium examples $120 or more depending on size, quality and locality.
What color is Satin Spar?
Satin Spar is most often white, cream, colorless, and peach. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
