igneous
Diorite
Diorite (Plagioclase feldspar and amphibole/biotite)
Hardness: 6-7 on the Mohs scale, Color: Salt and pepper appearance (black and white or grey speckled), Luster: Dull to sub-vitreous, Crystal structure: Phaneritic (coarse-grained, visible interlocking crystals), Specific Gravity: 2.7-2.9
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Physical properties
Hardness: 6-7 on the Mohs scale, Color: Salt and pepper appearance (black and white or grey speckled), Luster: Dull to sub-vitreous, Crystal structure: Phaneritic (coarse-grained, visible interlocking crystals), Specific Gravity: 2.7-2.9
Formation & geological history
Formed from the slow cooling of intermediate magma beneath the Earth's surface (intrusive igneous rock). Commonly found in continental volcanic arcs and mountain-building zones.
Uses & applications
Widely used as crushed stone in construction, dimension stone, building facades, and historically as carving stone by ancient civilizations such as the Maya and Egyptians.
Geological facts
Ancient civilizations often used diorite for art and architecture due to its extreme toughness and durability; the famous Code of Hammurabi is inscribed on a stele made of black diorite.
Field identification & locations
Can be identified in the field by its distinctive 'salt and pepper' texture with roughly equal amounts of dark ferromagnesian minerals and light plagioclase feldspar. Commonly found in glaciated regions and riverbeds as smoothed pebbles.
