sedimentary
Chert with Crinoid Fossil Impression
Microcrystalline Quartz (SiO2) with Crinoidea fossil impression
Hardness: 7 (Mohs scale); Color: Yellow-brown, tan, ochre; Luster: Waxy to dull; Structure: Cryptocrystalline/Amorphous; Conchoidal fracture; Opaque.
- Hardness
- 7 (Mohs scale)
- Color
- Yellow-brown, tan, ochre
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Yellow-brown, tan, ochre; Luster: Waxy to dull; Structure: Cryptocrystalline/Amorphous; Conchoidal fracture; Opaque.
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments during various geological eras (often Paleozoic for such fossils). This specimen shows a cast/impression of a crinoid stem segment.
Uses & applications
Used historically for stone tools due to conchoidal fracture; modern uses include landscaping and as collector specimens for paleontological interest.
Geological facts
Crinoids are also known as 'sea lilies,' though they are animals related to starfish rather than plants. Their segmented stems are one of the most common fossils found in sedimentary rocks.
Field identification & locations
Identify by its waxy luster, high hardness (will scratch glass), and the characteristic ribbed 'screw-thread' impression of a crinoid stem. Commonly found in limestone and shale deposits globally.
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