Phacops is a genus of trilobite known for its distinct large eyes and ability to roll into a ball as a defense mechanism. Collectors often prize specimens that are enrolled, displaying high levels of detail in the glabella and thoracic segments. They are commonly found in Paleozoic marine limestone and shale deposits worldwide.
Is this phacops?
3-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 phacops with a known reference. Phacops sits at Mohs 3-5 — softer than the next harder reference, harder than the previous one.
- 2Match the color rangeCompare against the expected color range: brown, gray, black.
- 3Look at form & habitTypical habit: trilobite fossil.
Often found alongside phacops
Minerals reported to co-occur with phacops. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Mohs hardness
- 3-5
- Transparency
- Opaque
- Crystal habit
- Trilobite Fossil
- Rarity
- Common
- Uses
- Collector, Decorative
- Host rock
- Sedimentary
- Typical price
- $10-500 depending on preservation and size
Where rockhounds find phacops
Classic worldwide localities
- Morocco
- USA (Ohio)
- Germany
- Canada (Ontario)
- United Kingdom
Field-hunting tip
Look in sedimentary country — that is the host setting where phacops typically forms. If you start seeing calcite, pyrite, limestone in float, you are in the right ground. Field specimens usually show a trilobite fossil habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find phacops on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
