Riversideite is a rare calcium silicate hydrate typically found as fine, silky, white fibrous masses in metamorphosed limestone environments. Collectors primarily look for it in classic localities like the Crestmore Quarry in California, where it often forms as a secondary mineral in altered limestone contact zones.
Is this riversideite?
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 riversideite with a known reference. Riversideite sits at Mohs 3 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Riversideite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Riversideite typically shows a silky luster.
- 4Match the color rangeCompare against the expected color range: white, colorless.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: fibrous aggregates, matted acicular crystals.
Often confused with
Riversideite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Luster reads silky on Riversideite and vitreous on Thaumasite.
How to tell apart: Luster reads silky on Riversideite and pearly on Gyrolite.
How to tell apart: Okenite is the harder of the two (Mohs 4.5-5 vs. 3); luster reads silky on Riversideite and pearly on Okenite.
Often found alongside riversideite
Minerals reported to co-occur with riversideite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₅Si₆O₁₈H₂·2H₂O
- Mohs hardness
- 3
- Density
- 2.2-2.3 g/cm³
- Streak
- White
- Luster
- Silky
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Fibrous Aggregates, Matted Acicular Crystals
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Metamorphosed Limestone
- Typical price
- $20-100 for small study specimens
Where rockhounds find riversideite
Classic worldwide localities
- Crestmore Quarry, California, USA
- Santa Lucia Mountains, California, USA
- Kola Peninsula, Russia
Field-hunting tip
Look in metamorphosed limestone country — that is the host setting where riversideite typically forms. If you start seeing calcite, tobermorite, afwillite in float, you are in the right ground. Field specimens usually show a fibrous aggregates, matted acicular crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find riversideite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
