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, 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.
