Rock Identifier
Andesite Porphyry (Geological Drill Core) (Andesite Porphyry) — igneous
igneous

Andesite Porphyry (Geological Drill Core)

Andesite Porphyry

Hardness: 6-7 (Mohs); Color: Greyish-green groundmass with white phenocrysts; Luster: Dull to sub-vitreous; Crystal Structure: Porphyritic (large crystals in fine matrix); Cleavage: None (individual minerals have cleavage); Specific Gravity: 2.5-2.8

Hardness
6-7 (Mohs)
Color
Greyish-green groundmass with white phenocrysts
Luster
Dull to sub-vitreous
Identified More igneous →

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Physical properties

Hardness: 6-7 (Mohs); Color: Greyish-green groundmass with white phenocrysts; Luster: Dull to sub-vitreous; Crystal Structure: Porphyritic (large crystals in fine matrix); Cleavage: None (individual minerals have cleavage); Specific Gravity: 2.5-2.8

Formation & geological history

Formed through volcanic activity at subduction zones where magma cools in two stages: slow cooling at depth (forming large phenocrysts) followed by rapid cooling during eruption (forming the fine-grained matrix).

Uses & applications

Used primarily as crushed stone for road construction, aggregate in concrete, and as industrial geological samples for mapping underground mineral deposits or bedrock stability.

Geological facts

This specific specimen is a 'drill core', a cylindrical sample removed from the earth by a diamond-tipped hollow drill bit during mineral exploration or geotechnical engineering.

Field identification & locations

Identified by the distinct white plagioclase feldspar laths embedded in a fine-grained, greenish-grey volcanic matrix. Drill cores like this are vital for locating gold, copper, and silver deposits.

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