igneous
Diorite (or Gabbro/Greenschist pebble)
Diorite (Plagioclase Feldspar with Hornblende/Biotite)
Hardness: 6-7 on Mohs scale. Color: Speckled green, dark grey, and white (salt-and-pepper texture). Luster: Dull to vitreous when wet/polished. Structure: Phaneritic (medium-grained interlocking crystals). Cleavage: Good in feldspar and amphibole minerals.
- Hardness
- 6-7 on Mohs scale
- Luster
- Dull to vitreous when wet/polished
Identified More igneous →
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Speckled green, dark grey, and white (salt-and-pepper texture). Luster: Dull to vitreous when wet/polished. Structure: Phaneritic (medium-grained interlocking crystals). Cleavage: Good in feldspar and amphibole minerals.
Formation & geological history
Formed through the slow cooling and crystallization of intermediate to mafic magma underground beneath volcanic arcs or continental crusts. Smooth, rounded shape indicates extensive stream, river, or beach erosion.
Uses & applications
Crushed stone for road construction, decorative landscaping, dimension stone for countertops and monuments, and popular among casual beach/river rock collectors.
Geological facts
Diorite is often called 'salt-and-pepper' rock due to its contrasting mixture of white plagioclase feldspar and dark amphibole or pyroxene minerals. Ancient Egyptians used hard diorite to carve statues and vases.
Field identification & locations
Identified by its characteristic interlocking 'salt-and-pepper' or greenish mottled texture in a water-worn pebble. Commonly found along rocky riverbeds, glacial tills, and marine pebble beaches globally.
