Basalt
Basalt (Aphanitic Igneous Rock) · Mineral Specimen / Common Rock
Crystal System
Microcrystalline (containing microscopic Orthorhombic and Monoclinic structures); Habit: Massive, vesicular, or columnar
Mineral Group
Silicates (primarily Plagioclase Feldspar and Pyroxene)
Chemical Formula
SiO2 (45–52%), Al2O3, CaO, FeO, MgO
Formation Process
Igneous: Forms from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface
About This Crystal
A fine-grained, dark-colored volcanic rock. This specimen is opaque with a dull to sub-vitreous luster and an earthy, rough surface texture with irregular fractured edges.
Physical Characteristics
Color: Dark grey to black; Streak: Grey; Cleavage: None (massive); Fracture: Conchoidal to uneven; Specific Gravity: 2.8–3.0; Magnetism: Often weakly magnetic due to magnetite content
Optical Properties
Generally opaque; individual crystals are too small to see with the naked eye; lacks notable optical phenomena like pleochroism in hand specimens
Hardness & Durability
Origin Region
Global; common in oceanic crust, volcanic islands (Hawaii, Iceland), and flood basalt plateaus
Hardness & Durability
Mohs hardness: 6.0; Toughness: Very High (extremely durable and resistant to crushing due to its dense, interlocking crystal structure)
Care & Maintenance
Highly durable; can be cleaned with water and mild soap; resistant to most environmental factors but can be etched by strong acids
Rarity & Value
Very Common; low commercial value as a mineral specimen; primarily valued as an industrial aggregate for construction and road shielding
Special Characteristics
May contain small vesicles (gas bubbles) or microscopic phenocrysts of olivine or plagioclase; notable for its high density and iron content
Lore & History
Historically used for early stone tools and monumental architecture (e.g., Rosetta Stone, Moai statues); traditionally associated with grounding and stability in metaphysical practices