Quartz concretions are rounded, compact masses of silica that often form within sedimentary layers like limestone or shale. Collectors often look for them as rounded rocks which, when broken open, may reveal a solid, banded, or drusy interior.
Is this quartz concretions?
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 quartz concretions with a known reference. Quartz Concretions sits at Mohs 7 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Quartz Concretions leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Quartz Concretions typically shows a dull to waxy luster.
- 4Match the color rangeCompare against the expected color range: white, gray, brown, tan.
- 5Look at form & habitCrystal system: trigonal. Typical habit: nodular, spherical, or concretionary masses.
Often confused with
Quartz Concretions vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside quartz concretions
Minerals reported to co-occur with quartz concretions. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- SiO₂
- Mohs hardness
- 7
- Density
- 2.65 g/cm³
- Streak
- White
- Luster
- Dull to Waxy
- Transparency
- Opaque
- Crystal system
- Trigonal
- Crystal habit
- Nodular, Spherical, Or Concretionary Masses
- Cleavage
- None
- Rarity
- Common
- Uses
- Collector, Lapidary
- Host rock
- Sedimentary Rock Environments
- Typical price
- $5-50 thumbnail/cabinet specimens
Where rockhounds find quartz concretions
2 mapped spotsClassic worldwide localities
- Missouri, USA
- Arkansas, USA
- South Dakota, USA
- France
- Germany
Field-hunting tip
Look in sedimentary rock environments country — that is the host setting where quartz concretions typically forms. If you start seeing calcite, dolomite, pyrite in float, you are in the right ground. Field specimens usually show a nodular, spherical, or concretionary masses habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Kansas, Nebraska — start trip planning there.
Common questions
How do you identify quartz concretions?+
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Can I find quartz concretions in the United States?+
How much is quartz concretions worth?+
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Find quartz concretions on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
