sedimentary
Ferruginous Sandstone (with possible trace fossils)
Arenite with Iron-Oxide Cement (SiO2 with Fe2O3)
Hardness: 6-7 (Mohs scale), Color: Rusty brown, tan, and dark orange, Luster: Dull/Earthy, Crystal Structure: Granular/Clastic, Cleavage: None, Specific Gravity: 2.6-2.8
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Physical properties
Hardness: 6-7 (Mohs scale), Color: Rusty brown, tan, and dark orange, Luster: Dull/Earthy, Crystal Structure: Granular/Clastic, Cleavage: None, Specific Gravity: 2.6-2.8
Formation & geological history
Formed in high-energy depositional environments like riverbeds or coastal zones where sand grains (quartz) were cemented together by iron-rich minerals over millions of years. This specimen shows signs of iron-oxide staining common in Paleozoic to Mesozoic strata.
Uses & applications
Used primarily in heavy construction, road base material, and historical building stone. Some varieties are crushed for silicate or iron extraction depending on purity.
Geological facts
The specimen features 'limonite' or 'hematite' staining, which often replaces or fills in organic molds. The irregular impressions on the surface are likely trace fossils (ichnofossils) or bioturbation from ancient burrowing organisms.
Field identification & locations
Identify in the field by its gritty sandpaper texture and orange-brown 'rust' streak. Common in the Appalachian region and Western US. Collectors should look for distinct shapes which may indicate fossils hidden within the matrix.
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