Silkstone is a fibrous, microcrystalline variety of quartz characterized by a unique, silky luster that arises from its dense, parallel fiber structure. It is a popular material for lapidary work and cabochons, often found in sedimentary deposits where silica has replaced other materials or filled veins.
Is this silkstone?
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 silkstone with a known reference. Silkstone sits at Mohs 7, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Silkstone leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Silkstone typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, gray, yellow.
- 5Look at form & habitCrystal system: trigonal. Typical habit: fibrous.
Often confused with
Silkstone vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside silkstone
Minerals reported to co-occur with silkstone. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- SiO₂
- Mohs hardness
- 7
- Density
- 2.65 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Fibrous
- Cleavage
- None
- Rarity
- Common
- Uses
- Lapidary, Collector, Decorative
- Host rock
- Sedimentary
- Typical price
- $5-50 for slabs and polished specimens
Where rockhounds find silkstone
Classic worldwide localities
- Australia
- USA
- Brazil
- Madagascar
Field-hunting tip
Look in sedimentary country, the host setting where silkstone typically forms. If you start seeing quartz, hematite, limonite in float, you are in the right ground. Field specimens usually show a fibrous habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find silkstone on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
