metamorphic

Weathered schist or foliated metamorphic rock

Mica-quartz schist, tentatively; mineral composition likely quartz, mica, and feldspar

AI-generated identification · may be incorrect

Gray, fine- to medium-grained, with weakly visible foliation and sparkly mica surfaces; uneven fracture and dull to slightly silky luster. Typical hardness is about 2–7 depending on the mineral tested; density commonly 2.6–2.8 g/cm³.

Identified September 17, 2026More metamorphic →

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At a glance

Common name: Weathered schist or foliated metamorphic rock
Scientific name: Mica-quartz schist, tentatively; mineral composition likely quartz, mica, and feldspar
Category: metamorphic
Identified: September 17, 2026
Method: Standard

AI Estimated Value

Typically $1–$10 as an ordinary field specimen; up to about $10–$30 if unusually fresh, strongly foliated, or visually attractive.

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

Formed when shale or another clay-rich sediment was buried and metamorphosed under elevated pressure and temperature, producing aligned mica. The specimen’s exact age cannot be determined visually; schist is common in ancient metamorphic terranes.

Uses & applications

Used locally as decorative stone, landscaping rock, aggregate, and occasionally building stone; attractive mica-rich pieces may be collected but are generally not gem material.

Geological facts

The layered texture is caused by foliation rather than sedimentary bedding. A steel nail may scratch mica-rich areas but usually will not scratch quartz grains.

Field identification & locations

The Santa Maria–Lompoc region can contain metamorphic and mélange-derived cobbles, so this is regionally plausible, though the photograph is insufficient for a precise species identification. Look for flakes that separate along layers; a streak test, hand lens, and hardness test would help distinguish schist from slate, phyllite, or weathered gneiss.