A chalcedony geode consists of a hollow rock cavity lined with a layer of microcrystalline silica, often exhibiting botryoidal or crusty habits. These specimens are highly prized by collectors for the contrast between the rough exterior rind and the smooth, often colorful or drusy interior lining.
Is this chalcedony geode?
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 chalcedony geode with a known reference. Chalcedony Geode sits at Mohs 6.5-7 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Chalcedony Geode leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Chalcedony Geode typically shows a waxy luster.
- 4Match the color rangeCompare against the expected color range: white, gray, blue, brown, colorless.
- 5Look at form & habitCrystal system: trigonal. Typical habit: botryoidal.
Often confused with
Chalcedony Geode vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside chalcedony geode
Minerals reported to co-occur with chalcedony geode. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- SiO₂
- Mohs hardness
- 6.5-7
- Density
- 2.55-2.65 g/cm³
- Streak
- White
- Luster
- Waxy
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Botryoidal
- Cleavage
- None
- Rarity
- Common
- Uses
- Collector, Lapidary, Decorative
- Host rock
- Sedimentary Limestone or Volcanic Basalt Cavities
- Typical price
- $10-50 thumbnail, $100-500 cabinet specimen
Where rockhounds find chalcedony geode
4 mapped spotsClassic worldwide localities
- Keokuk, Iowa
- Illinois, USA
- Durango, Mexico
- Morocco
- Brazil
Field-hunting tip
Look in sedimentary limestone or volcanic basalt cavities country — that is the host setting where chalcedony geode typically forms. If you start seeing quartz, calcite, goethite in float, you are in the right ground. Field specimens usually show a botryoidal habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Arizona, Michigan, Oregon — start trip planning there.
Common questions
How do you identify chalcedony geode?+
Where is chalcedony geode found?+
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Find chalcedony geode on the map
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