metamorphic

Pyrite-bearing dark metamorphic rock, likely schist or hornfels

Quartz–feldspar–mica matrix with pyrite (FeS₂); exact identification requires testing

AI-generated identification · may be incorrect

Dark gray to black, fine-grained and weakly foliated, with brassy metallic pyrite flakes or crystals. Pyrite hardness is 6–6.5 Mohs and cubic crystals are common; the host rock appears harder than glass but has no obvious cleavage.

Identified September 17, 2026More metamorphic →

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At a glance

Common name: Pyrite-bearing dark metamorphic rock, likely schist or hornfels
Scientific name: Quartz–feldspar–mica matrix with pyrite (FeS₂); exact identification requires testing
Category: metamorphic
Identified: September 17, 2026
Method: Standard

AI Estimated Value

About $5–$30 for a common rough specimen; $30–$100+ if crystals are abundant, well formed, or from a documented locality.

Not an official valuation

AI estimate for general interest only — not an appraisal. Actual value depends on condition, provenance, and market demand. Verify with a professional before buying, selling, or insuring.

This identification was generated by AI and may contain errors. Verify important details before relying on them — and never use an AI result to judge whether a specimen is safe to handle. Read the full disclaimer

Physical properties

Formation & geological history

Likely formed when sulfur- and iron-bearing sediments or volcanic rocks were metamorphosed, allowing pyrite to crystallize; age cannot be determined from the image. Similar rocks occur in hydrothermal and contact-metamorphic zones.

Uses & applications

Primarily a collector specimen; pyrite may be mined for sulfur or historically for sulfuric-acid production, while the host rock has limited construction value. It is generally unsuitable for jewelry because pyrite tarnishes and can weather.

Geological facts

The brassy grains are most likely pyrite (“fool’s gold”), though chalcopyrite is a possible alternative. Pyrite commonly develops a dark oxidation coating and may produce sulfuric acid during weathering.

Field identification & locations

Check for a metallic luster, opaque brassy color, and a dark streak: pyrite streaks greenish-black, whereas gold streaks yellow. A steel-file test, streak plate, magnet test, and close inspection for cubic crystals can distinguish pyrite from other sulfides.