Whewellite is a rare calcium oxalate mineral typically found in coal seams or hydrothermal ore veins. It is highly valued by collectors for its transparent, well-defined monoclinic crystals which often exhibit complex twinning.
Is this whewellite?
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 whewellite with a known reference. Whewellite sits at Mohs 2.5-3 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Whewellite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Whewellite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white, yellowish, brownish.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular to prismatic crystals, often twinned.
Often confused with
Whewellite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside whewellite
Minerals reported to co-occur with whewellite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca(C₂O₄)·H₂O
- Mohs hardness
- 2.5-3
- Density
- 2.23 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular to Prismatic Crystals, Often Twinned
- Cleavage
- Perfect On {010}
- Fluorescence
- Often Exhibits White, Yellow, Or Blue Fluorescence Under UV Light
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- Hydrothermal Veins and Sedimentary Coal Deposits
- Typical price
- $20-150 for good thumbnail or miniature specimens
Where rockhounds find whewellite
1 mapped spotsClassic worldwide localities
- Czech Republic
- Germany
- United States
- Hungary
- Russia
Field-hunting tip
Look in hydrothermal veins and sedimentary coal deposits country — that is the host setting where whewellite typically forms. If you start seeing calcite, barite, sphalerite in float, you are in the right ground. Field specimens usually show a tabular to prismatic crystals, often twinned habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in South Dakota — start trip planning there.
Common questions
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Find whewellite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
