Cold Water Agate is a variety of chalcedony found primarily in the Coldwater Formation of Michigan, occurring as nodules within sedimentary rock. Collectors prize it for its subtle banding and earthy color, best revealed after tumbling or slabbing for lapidary work.
Is this cold water agate?
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 cold water agate with a known reference. Cold Water Agate 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. Cold Water Agate leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Cold Water Agate typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: gray, white, yellow, orange, red, brown.
- 5Look at form & habitCrystal system: trigonal. Typical habit: nodular.
Often confused with
Cold Water Agate vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads vitreous on Cold Water Agate and waxy on Flint Nodule.
How to tell apart: Luster reads vitreous on Cold Water Agate and waxy on Chalcedony.
How to tell apart: Luster reads vitreous on Cold Water Agate and waxy on Jasper.
Often found alongside cold water agate
Minerals reported to co-occur with cold water agate. 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
- 2.6-2.7 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Nodular
- Cleavage
- None
- Rarity
- Common
- Uses
- Lapidary, Collector, Decorative
- Host rock
- Sedimentary
Where rockhounds find cold water agate
18 mapped spotsClassic worldwide localities
- Michigan, USA
- Ontario, Canada
- Lake Huron Basin
U.S. states with cold water agate
Each link opens a state-specific list of mapped rockhounding spots that produce cold water agate.
Field-hunting tip
Look in sedimentary country, the host setting where cold water agate typically forms. If you start seeing calcite, dolomite, quartz in float, you are in the right ground. Field specimens usually show a nodular habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Michigan, Wisconsin, Iowa. Start trip planning there.
More cold water agate photos
Common questions
How do you identify cold water agate?+
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Find cold water agate on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
