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.
- 2Name the organismDecide what left the fossil before worrying about the rock. Organism: Trilobite (genus Phacops; North American species now Eldredgeops). Age: Late Ordovician to the end of the Devonian.
- 3Match the color rangeCompare against the expected color range: brown, gray, black.
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
- Rarity
- Common
- Uses
- Collector, Decorative
- Host rock
- sedimentary
- Organism
- Trilobite (genus Phacops; North American species now Eldredgeops)
- Age
- Late Ordovician to the end of the Devonian
Where rockhounds find phacops
Classic worldwide localities
- Morocco
- USA (Ohio)
- Germany
- Canada (Ontario)
- United Kingdom
Field-hunting tip
Where it forms: sedimentary. If you start seeing calcite, pyrite, limestone in float, you are in the right ground.
Common questions
How do you identify phacops?+
Where is phacops found?+
What minerals are found with phacops?+
What kind of rock does phacops form in?+
What is phacops used for?+
Find phacops on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
