igneous
Diorite
Diorite (Intermediate intrusive igneous rock)
Hardness: 6-7 on Mohs scale. Color: Spotted 'salt and pepper' appearance (black and white/grey). Luster: Phaneritic (visible crystals), dull to vitreous. Crystal structure: Coarse-grained. Cleavage: Good in two directions (due to feldspar). Specific gravity: 2.8-3.0.
- Hardness
- 6-7 on Mohs scale
- Color
- Spotted 'salt and pepper' appearance (black and white/grey)
- Luster
- Phaneritic (visible crystals), dull to vitreous
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Spotted 'salt and pepper' appearance (black and white/grey). Luster: Phaneritic (visible crystals), dull to vitreous. Crystal structure: Coarse-grained. Cleavage: Good in two directions (due to feldspar). Specific gravity: 2.8-3.0.
Formation & geological history
Formed by the slow cooling of magma deep beneath the Earth's surface (intrusive). Usually associated with convergent plate boundaries and volcanic arcs. Can be found in many Precambrian and Paleozoic mountain ranges.
Uses & applications
Used primarily in construction for crushed stone, base material for roads, and as a dimension stone for building facades, floor tiles, and grave markers. Occasionally used for sculptures.
Geological facts
Diorite is so hard that ancient civilizations, like the Egyptians, used it as tools to work on softer stones like granite. The Code of Hammurabi was inscribed on a large pillar of diorite.
Field identification & locations
Identify in the field by its speckled 'salt and pepper' look, lack of visible quartz (unlike granite), and coarse grain. Found in batholiths and mountainous regions worldwide (e.g., Andes, Alps). Collectors look for uniform texture and lack of weathering.
