Basalt Fragment
Extrusive Igneous Rock / Basalt · Mineral Specimen / Rock
Crystal System
Amorphous to Microcrystalline (Individual mineral components crystallize in Monoclinic, Triclinic, and Orthorhombic systems)
Mineral Group
Silicate Rock (Igneous)
Chemical Formula
Complex silicate mixture containing plagioclase feldspar, pyroxene, and olivine
Formation Process
Igneous process formed by the rapid cooling of low-viscosity, iron- and magnesium-rich lava at or near the Earth's surface
About This Crystal
A dark gray to black, fine-grained rock fragment held in a hand. It exhibits a dull to sub-vitreous luster with a rough, weathered surface texture typical of weathered volcanic fragments.
Physical Characteristics
Dark gray to black body color; white to gray streak for powdered components; aphanitic (fine-grained) habit; no distinct cleavage; uneven to conchoidal fracture; specific gravity typically ranges around 2.8 to 3.0; brittle tenacity; non-magnetic generally, though may contain minor magnetite.
Optical Properties
Opaque in hand specimen; thin sections viewed under petrographic microscope show double refraction in individual mineral grains (plagioclase, pyroxene).
Hardness & Durability
Origin Region
Worldwide distribution, associated with volcanic regions, oceanic crust, and continental flood basalts
Hardness & Durability
Mohs hardness typically 5 to 6 for the bulk rock, depending on constituent mineral proportions. Good toughness and physical stability under normal environmental conditions.
Care & Maintenance
Clean with warm water and mild soap if needed; highly durable against water, heat, and light, though porous weathered surfaces can trap dirt.
Rarity & Value
Very common; basalt is the most common rock type in the Earth's crust, particularly forming the oceanic floor. Valued primarily as a geological or educational specimen rather than a gemstone, with very low commercial monetary value.
Special Characteristics
May exhibit vesicular texture (gas bubbles trapped during cooling) or porphyritic texture (larger crystals called phenocrysts embedded in the fine-grained matrix), though this specific sample appears fine-grained and weathered.
Lore & History
Historically used by ancient civilizations for stone tools, grinding stones, and construction materials due to its density and durability. In modern metaphysical practices, volcanic rocks like basalt and lava stone are used for grounding, stability, and calming emotional intensity, though these are traditional beliefs and not scientific claims.