sedimentary
Limestone with fossil crinoid stems
Calcium Carbonate (CaCO3) containing Crinoidea fossils
Hardness: 3 on Mohs scale; Color: light grey to buff; Luster: earthy to dull; Crystal structure: microcrystalline calcite with visible biological structures; Cleavage: none in mass, but rhombohedral in calcite crystals.
- Hardness
- 3 on Mohs scale
- Color
- light grey to buff
- Luster
- earthy to dull
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Physical properties
Hardness: 3 on Mohs scale; Color: light grey to buff; Luster: earthy to dull; Crystal structure: microcrystalline calcite with visible biological structures; Cleavage: none in mass, but rhombohedral in calcite crystals.
Formation & geological history
Formed in warm, shallow marine environments through the accumulation of skeletal fragments of marine organisms. These crinoid-rich limestones are often from the Paleozoic era (approx. 250-540 million years ago).
Uses & applications
Used primarily in the construction industry as building stone, road base, and in the production of cement and lime. Significant as a geological record for paleontology.
Geological facts
Crinoids are also known as 'sea lilies' and are echinoderms, related to starfish and sea urchins. Although they look like plants, they are actually animals.
Field identification & locations
Identify in the field by looking for segmented, 'bolt-like' or 'cheerio-like' cylinder shapes within the rock matrix. It will react and fizz strongly when exposed to a drop of weak acid such as vinegar or HCl.
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