igneous

Porphyritic basalt (likely hornblende- or pyroxene-rich)

Porphyritic mafic volcanic rock; fine-grained basaltic groundmass with larger dark ferromagnesian and pale plagioclase crystals

AI-generated identification · may be incorrect

Typically dark gray to black, with contrasting gray-white plagioclase and dark pyroxene/amphibole phenocrysts; generally hard (about Mohs 6), dull to faintly vitreous, dense, and massive. The visible coarse crystals suggest porphyritic texture, though the specimen may also be a fine-grained gabbro or diabase.

Identified September 10, 2026More igneous →

Explore Porphyritic basalt (likely hornblende- or pyroxene-rich) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

At a glance

Common name: Porphyritic basalt (likely hornblende- or pyroxene-rich)
Scientific name: Porphyritic mafic volcanic rock; fine-grained basaltic groundmass with larger dark ferromagnesian and pale plagioclase crystals
Category: igneous
Identified: September 10, 2026
Method: Standard

AI Estimated Value

$5–$25 typical hand specimen; $25–$75 for attractive or documented material

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 mafic magma cooled relatively quickly near or at Earth’s surface, after earlier crystal growth at depth; commonly Cenozoic to Precambrian in age depending on locality. Exact identification requires a fresh surface, thin section, or mineral tests.

Uses & applications

Used as crushed aggregate, road stone, riprap, and occasionally building stone; attractive polished pieces are collected but have modest commercial value.

Geological facts

The pale crystals are probably calcium-rich plagioclase, while the dark grains are likely pyroxene or amphibole. Basaltic rocks are among Earth’s most abundant crustal rocks and commonly form oceanic crust.

Field identification & locations

Identify by its dark, heavy matrix, interlocking crystals, and lack of obvious layering or foliation; common in volcanic regions and continental flood-basalt provinces. Approximate value: $5–$25 for a typical hand specimen, or $25–$75 if unusually attractive or locality-labeled.