Cryptochalcite is a name sometimes applied to microcrystalline or cryptocrystalline forms of calcite that lack well-developed visible crystal faces. It typically appears as dull, massive material found in sedimentary environments or as a secondary precipitate in cavities. Because it is chemically identical to common calcite, it is best identified through its reaction with dilute hydrochloric acid and its lack of visible crystal structure.
Is this cryptochalcite?
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 cryptochalcite with a known reference. Cryptochalcite 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. Cryptochalcite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Cryptochalcite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, gray, yellowish.
- 5Look at form & habitCrystal system: trigonal. Typical habit: massive.
Often confused with
Cryptochalcite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside cryptochalcite
Minerals reported to co-occur with cryptochalcite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaCO₃
- Mohs hardness
- 3
- Density
- 2.71 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Massive
- Cleavage
- Perfect Rhombohedral
- Rarity
- Common
- Uses
- Collector, Educational
- Host rock
- Sedimentary
- Typical price
- $5-20
Where rockhounds find cryptochalcite
Classic worldwide localities
- Mexico
- USA
- Germany
- Italy
Field-hunting tip
Look in sedimentary country — that is the host setting where cryptochalcite typically forms. If you start seeing calcite, dolomite, quartz in float, you are in the right ground. Field specimens usually show a massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify cryptochalcite?+
Where is cryptochalcite found?+
How much is cryptochalcite worth?+
What rocks look like cryptochalcite?+
What minerals are found with cryptochalcite?+
What kind of rock does cryptochalcite form in?+
What is cryptochalcite used for?+
Find cryptochalcite on the map
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