Silhydrite is a rare hydrous silicon dioxide mineral that forms as soft, platy, or micaceous aggregates. It is typically found in minor hydrothermal deposits and is known for its low specific gravity and distinct pearly luster. Collectors often seek it due to its limited occurrences and association with unique silica-rich environments.
Is this silhydrite?
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 silhydrite with a known reference. Silhydrite sits at Mohs 1-2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Silhydrite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Silhydrite typically shows a pearly luster.
- 4Match the color rangeCompare against the expected color range: white, colorless.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: platy crystals, crusts.
Often confused with
Silhydrite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Opal is the harder of the two (Mohs 5.5-6.5 vs. 1-2); luster reads pearly on Silhydrite and vitreous on Opal.
How to tell apart: Chalcedony is the harder of the two (Mohs 6.5-7 vs. 1-2); luster reads pearly on Silhydrite and waxy on Chalcedony.
How to tell apart: Luster reads pearly on Silhydrite and dull on Montmorillonite.
Often found alongside silhydrite
Minerals reported to co-occur with silhydrite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- 3SiO₂·H₂O
- Mohs hardness
- 1-2
- Density
- 1.97 g/cm³
- Streak
- White
- Luster
- Pearly
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Platy Crystals, Crusts
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins
- Typical price
- $20-100 thumbnail specimen
Where rockhounds find silhydrite
Classic worldwide localities
- Fairview mine, California, USA
- Nevada, USA
Field-hunting tip
Look in hydrothermal veins country — that is the host setting where silhydrite typically forms. If you start seeing quartz, opal, calcite in float, you are in the right ground. Field specimens usually show a platy crystals, crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find silhydrite on the map
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