mineral
Yellow jasper (likely iron-stained chert or quartzite)
Microcrystalline quartz, SiO₂, colored by iron oxides/hydroxides
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; opaque mustard-yellow to brown, earthy/waxy luster, very fine-grained crystalline structure, and no visible cleavage. It should produce a sharp edge and scratch glass, though the rounded surface suggests tumbling or water wear.
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Physical properties
Hardness about 6.5–7 Mohs; opaque mustard-yellow to brown, earthy/waxy luster, very fine-grained crystalline structure, and no visible cleavage. It should produce a sharp edge and scratch glass, though the rounded surface suggests tumbling or water wear.
Formation & geological history
Forms when silica-rich fluids replace or cement sediments, with iron staining producing the yellow coloration; commonly Paleozoic to younger, though age cannot be determined visually. The specimen appears naturally rounded or polished.
Uses & applications
Used as a lapidary and decorative stone for cabochons, beads, carvings, and tumbled stones; occasionally used as aggregate or ornament. Common pieces generally have modest collector value.
Geological facts
Jasper is an opaque variety of chalcedony or microcrystalline quartz, and color patterns often reflect changing iron-rich fluids during formation.
Field identification & locations
Common in volcanic and sedimentary terrains worldwide, including the western United States, Brazil, India, Madagascar, and Australia. Confirm with a glass-scratch test, streak test, and close inspection for a conchoidal fracture; avoid confusing it with yellow calcite, which is softer.
