metamorphic
Iron-oxide-stained quartz-rich rock (likely ironstone or ferruginous quartzite)
Ferruginous quartzite; predominantly quartz (SiO₂) with iron oxides/hydroxides such as hematite and goethite
AI-generated identification · may be incorrectRounded, ochre-brown specimen with a granular, locally sparkly surface and rusty iron staining. Quartz is Mohs 7 with a vitreous luster and no cleavage; iron oxides commonly produce yellow, orange, and brown colors. Specific gravity varies with iron content, roughly 2.6–4.
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Physical properties
Rounded, ochre-brown specimen with a granular, locally sparkly surface and rusty iron staining. Quartz is Mohs 7 with a vitreous luster and no cleavage; iron oxides commonly produce yellow, orange, and brown colors. Specific gravity varies with iron content, roughly 2.6–4.
Formation & geological history
Likely formed when silica-rich sediment or rock was cemented or altered by iron-rich fluids; if metamorphosed, heat and pressure recrystallized the quartz. The image alone cannot establish its age or exact origin.
Uses & applications
Usually collected as a field specimen; iron-rich varieties may be sources of iron ore, while quartzite is used as aggregate or dimension stone. This small rough piece has little jewelry value.
Geological facts
Rust-colored streaks or coatings commonly result from goethite and hematite. The rounded shape suggests weathering or transport, but does not identify a specific rock type.
Field identification & locations
Look for a hard, gritty surface and quartz grains; a streak test and hardness test can help distinguish it from softer ironstone. Quartz-rich rocks occur worldwide; value is typically about $1–$10 for a common hand specimen.
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