igneous
Diorite (Dalmatian Stone)
Intermediate Phaneritic Igneous Rock
Hardness: 6-7 Mohs; Color: Black and white speckled; Luster: Sub-vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Composition: Plagioclase feldspar, hornblende, and biotite.
- Hardness
- 6-7 Mohs
- Color
- Black and white speckled
- Luster
- Sub-vitreous to dull
Identified More igneous →
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Physical properties
Hardness: 6-7 Mohs; Color: Black and white speckled; Luster: Sub-vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Composition: Plagioclase feldspar, hornblende, and biotite.
Formation & geological history
Formed by the slow cooling of magma beneath the Earth's surface (intrusive) in volcanic arcs and subduction zones. It has a chemical composition intermediate between granite and gabbro.
Uses & applications
Commonly used as a base material in construction (crushed stone), for cemetery markers, and polished for use as a decorative gemstone known as Dalmatian Stone in jewelry.
Geological facts
Diorite was used in ancient Egypt for carving hard statues due to its extreme durability. The famous Code of Hammurabi is inscribed on a diorite stele.
Field identification & locations
Identified by its distinctive 'salt and pepper' appearance. Look for even distributions of dark and light minerals without the visible quartz typical of granite. Common in mountainous regions with historical subduction activity.
