Satin Spar is a fibrous, silky variety of gypsum that exhibits a distinct chatoyancy or cat's-eye effect when polished. It is typically found in sedimentary evaporite beds, often occurring as compact, parallel fibrous veins.
Is this satin spar?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch satin spar with a known reference. Satin Spar sits at Mohs 2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: silky.
- 4Match the color rangeCompare against the expected color range: white, colorless, gray.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: fibrous.
Often confused with
Satin Spar vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside satin spar
Minerals reported to co-occur with satin spar. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaSO₄·2H₂O
- Mohs hardness
- 2
- Density
- 2.3 g/cm³
- Streak
- White
- Luster
- Silky
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Fibrous
- Cleavage
- Perfect in one direction
- Rarity
- Common
- Uses
- Collector, Lapidary, Decorative
- Host rock
- sedimentary evaporite deposits
Where rockhounds find satin spar
1 mapped spotsClassic worldwide localities
- United Kingdom
- USA
- Mexico
- Poland
- Italy
Field-hunting tip
Where it forms: sedimentary evaporite deposits. If you start seeing anhydrite, halite, sulfur in float, you are in the right ground. Typical habit: fibrous. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in New Mexico. Start trip planning there.
Common questions
How do you identify satin spar?+
Where is satin spar found?+
Can I find satin spar in the United States?+
What rocks look like satin spar?+
What minerals are found with satin spar?+
What kind of rock does satin spar form in?+
What is satin spar used for?+
Find satin spar on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
