igneous
Diorite
Intermediate Intrusive Igneous Rock
Hardness: 6-7 on Mohs scale. Color: Speckled black and white ('salt and pepper' appearance). Luster: Dull to vitreous. Texture: Phaneritic (medium- to coarse-grained). Cleavage: Good in amphibole/feldspar grains. Specific Gravity: 2.8 - 3.0.
- Hardness
- 6-7 on Mohs scale
- Color
- Speckled black and white ('salt and pepper' appearance)
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Speckled black and white ('salt and pepper' appearance). Luster: Dull to vitreous. Texture: Phaneritic (medium- to coarse-grained). Cleavage: Good in amphibole/feldspar grains. Specific Gravity: 2.8 - 3.0.
Formation & geological history
Formed by the slow cooling of magma deep beneath the Earth's surface (plutonic) in subduction zones and mountain-building regions. Composed primarily of plagioclase feldspar, hornblende, pyroxene, and sometimes small amounts of quartz.
Uses & applications
Used in construction as crushed stone, dimension stone for buildings and monuments, decorative landscaping, and historically for sculptures (such as the Code of Hammurabi).
Geological facts
Diorite was widely used in ancient civilizations like Mesopotamia and Ancient Egypt for carving statues and inscriptions because of its extreme hardness and durability.
Field identification & locations
Identified by its distinctive speckled 'salt and pepper' pattern with approximately equal amounts of light-colored feldspar and dark-colored ferromagnesian minerals. Commonly found in volcanic arcs and continental mountain ranges worldwide.
