igneous
Diorite with Quartz Vein
Intermediate plutonic igneous rock (Diorite / Metagabbro with SiO2 quartz alteration)
Hardness: 6-7 on Mohs scale. Color: Dark greyish-green to black groundmass with speckled white plagioclase feldspar and a distinct milky white quartz vein. Luster: Dull to vitreous on fresh surfaces. Texture: Phaneritic (medium to coarse-grained). Specific gravity: 2.8 - 3.0.
- Hardness
- 6-7 on Mohs scale
- Luster
- Dull to vitreous on fresh surfaces
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Dark greyish-green to black groundmass with speckled white plagioclase feldspar and a distinct milky white quartz vein. Luster: Dull to vitreous on fresh surfaces. Texture: Phaneritic (medium to coarse-grained). Specific gravity: 2.8 - 3.0.
Formation & geological history
Formed through the slow cooling of intermediate magma deep within the Earth's crust (plutonic igneous origin), typically at convergent plate boundaries and subduction zones. The white vein formed later via hydrothermal fluids depositing quartz into fractures within the cooling rock mass.
Uses & applications
Diorite is primarily used as crushed stone for construction, road base, and concrete aggregate. High-grade polished diorite is used as dimensional stone, building facades, and countertops. Ancient civilizations, such as the Mesopotamians and Egyptians, used diorite for durable stone carvings, steles (such as the Code of Hammurabi), and sculptures.
Geological facts
Diorite is often described as having a 'salt and pepper' appearance due to the mix of white feldspar and dark amphibole or pyroxene minerals. The white quartz vein running through this specimen shows evidence of post-magmatic hydrothermal activity.
Field identification & locations
Look for a coarse-grained rock with a roughly equal balance of light plagioclase feldspar and dark ferromagnesian minerals (hornblende, augite, biotite), distinguishable from granite by the relative lack of pink orthoclase feldspar. Widely found in mountain roots, volcanic arcs, and batholith complexes globally.
