igneous
Diorite (Dalmatian Stone variant)
Phaneritic Intermediate Plutonic Rock (Diorite)
Hardness: 6-7 on Mohs scale; Color: Mottled black and white (salt and pepper); Luster: Dull to sub-vitreous; Structure: Phaneritic (coarse-grained crystals); Cleavage: Two directions (from amphibole/feldspar).
- Hardness
- 6-7 on Mohs scale
- Color
- Mottled black and white (salt and pepper)
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Mottled black and white (salt and pepper); Luster: Dull to sub-vitreous; Structure: Phaneritic (coarse-grained crystals); Cleavage: Two directions (from amphibole/feldspar).
Formation & geological history
Formed by the slow cooling of silica-intermediate magma beneath the Earth's surface (intrusive). Commonly found in volcanic arcs and mountain-building zones (cordilleran margins).
Uses & applications
Used as a crushed stone for construction, road base, and drainage. High-quality specimens are polished for use as countertops, floor tiles, and ornamental carvings often sold as 'Dalmatian Stone'.
Geological facts
Diorite was used by Ancient Egyptians for statues and vases because of its extreme hardness; the Code of Hammurabi was famously inscribed on a large diorite stele.
Field identification & locations
Identified by its 'salt and pepper' appearance with roughly equal parts light plagioclase feldspar and dark minerals like hornblende or biotite. It lacks the visible quartz typical of granite.
