Chalcedony nodules typically form as rounded, botryoidal masses within rock cavities or as sedimentary concretions. They are recognized by their waxy luster, lack of visible crystalline structure to the naked eye, and characteristic smooth, mammillary surface texture.
Is this chalcedony nodules?
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 nodules with a known reference. Chalcedony Nodules 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 Nodules leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Chalcedony Nodules typically shows a waxy luster.
- 4Match the color rangeCompare against the expected color range: white, gray, blue, brown, tan.
- 5Look at form & habitCrystal system: trigonal. Typical habit: botryoidal.
Often confused with
Chalcedony Nodules vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Luster reads waxy on Chalcedony Nodules and vitreous on Opal.
How to tell apart: Chalcedony Nodules is noticeably harder (Mohs 6.5-7 vs. 4-4.5); luster reads waxy on Chalcedony Nodules and vitreous on Smithsonite.
How to tell apart: Luster reads waxy on Chalcedony Nodules and vitreous on Prehnite.
Often found alongside chalcedony nodules
Minerals reported to co-occur with chalcedony nodules. 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
- 2.6-2.65 g/cm³
- Streak
- White
- Luster
- Waxy
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Botryoidal
- Cleavage
- None
- Rarity
- Common
- Uses
- Lapidary, Collector, Decorative
- Host rock
- Sedimentary and Volcanic Cavities
- Typical price
- $5-50 thumbnail, $50-200 display specimen
Where rockhounds find chalcedony nodules
2 mapped spotsClassic worldwide localities
- USA
- Mexico
- Brazil
- India
- Madagascar
Field-hunting tip
Look in sedimentary and volcanic cavities country — that is the host setting where chalcedony nodules 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 Tennessee, Washington — start trip planning there.
Common questions
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Find chalcedony nodules on the map
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