igneous
Basalt with Epidote
Mafic volcanic rock with Epidote (Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH))
Hardness: 5-7 (Mohs scale); Color: Gray-black with greenish patches; Luster: Dull to vitreous; Crystal structure: Aphanitic (fine-grained) with secondary monoclinic coatings; Specific Gravity: 2.8-3.3
- Hardness
- 5-7 (Mohs scale)
- Color
- Gray-black with greenish patches
- Luster
- Dull to vitreous
Identified More igneous →
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Physical properties
Hardness: 5-7 (Mohs scale); Color: Gray-black with greenish patches; Luster: Dull to vitreous; Crystal structure: Aphanitic (fine-grained) with secondary monoclinic coatings; Specific Gravity: 2.8-3.3
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava. The greenish tint indicates hydrothermal alteration where epidote replaces original minerals like plagioclase or pyroxene.
Uses & applications
Commonly used as crushed stone for road base, concrete aggregate, and railroad ballast. Decorative specimens are used in landscaping or small mineral collections.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor; epidote is often a sign of low-grade metamorphism.
Field identification & locations
Identify by its dark core, fine grain, and weight. Greenish surfaces that don't scrub off are usually the epidote mineral. Found globally in volcanic regions like the Pacific Northwest or Iceland.
