igneous
Red Porphyry
Porphyritic Andesite or Rhyolite
AI-generated identification · may be incorrectHardness: 6-7 (Mohs scale); Color: Dark red to maroon groundmass with white or light-colored phenocrysts; Luster: Dull to sub-vitreous; Structure: Porphyritic (large crystals in a fine-grained matrix); Cleavage: None (conchoidal fracture).
- Hardness
- 6-7 (Mohs scale)
- Luster
- Dull to sub-vitreous
Identified More igneous →
Explore Red Porphyry in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6-7 (Mohs scale); Color: Dark red to maroon groundmass with white or light-colored phenocrysts; Luster: Dull to sub-vitreous; Structure: Porphyritic (large crystals in a fine-grained matrix); Cleavage: None (conchoidal fracture).
Formation & geological history
Formed through a two-stage cooling process of silica-rich magma; large crystals (phenocrysts) formed slowly at depth, followed by rapid cooling of the remaining melt near the surface. Often associated with volcanic arcs and Precambrian or Paleozoic geological ages.
Uses & applications
Used historically as a prestigious building material, for sculpture, and in modern times for high-end countertops, decorative paving, and crushed stone for road construction.
Geological facts
In antiquity, 'Imperial Porphyry' from Egypt was the most prestigious stone in the Roman Empire, reserved exclusively for the Emperor's use due to its purple-red color, which symbolized royalty.
Field identification & locations
Identify by looking for distinct, light-colored blocky crystals (usually feldspar) embedded in a uniform, fine-grained reddish background. Commonly found in glaciated regions as 'erratics' or near ancient volcanic sites. Collectors value well-worn river or beach cobbles for their aesthetic pattern.
