sedimentary
Quartz-encrusted Matrix
Silicon Dioxide (SiO2) with Ferruginous Sandstone
Hardness (Quartz): 7 Mohs, Color: tan with red/brown iron oxides, Luster: vitreous to earthy, Crystal Structure: hexagonal (trigonal) in quartz patches, Cleavage: poor/conchoidal
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Physical properties
Hardness (Quartz): 7 Mohs, Color: tan with red/brown iron oxides, Luster: vitreous to earthy, Crystal Structure: hexagonal (trigonal) in quartz patches, Cleavage: poor/conchoidal
Formation & geological history
Formed through secondary mineralization where silica-rich fluids precipitated quartz into the voids of a sedimentary host rock, likely during the Phanerozoic eon.
Uses & applications
Primarily of value to amateur geologists and hobbyists for collection and education; no significant industrial application.
Geological facts
The reddish-brown staining is evidence of iron oxidation (hematite or limonite), which often occurs in oxidizing terrestrial environments near the surface.
Field identification & locations
Identify by its ability to scratch glass (due to quartz content) and its gritty, granular texture in the non-crystallized areas. Common in arid or weathered sedimentary outcrops.
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