Basalt
Extrusive Igneous Rock / Basalt · Mineral Specimen / Industrial Rock
Crystal System
Amorphous to microcrystalline, aphanitic texture
Mineral Group
Silicates (specifically mafic igneous rock)
Chemical Formula
Complex silicate melt solution containing SiO2, Al2O3, FeO, MgO, CaO, Na2O
Formation Process
Igneous, formed by the rapid cooling of low-viscosity, iron- and magnesium-rich lava flows at or near the Earth's surface
About This Crystal
An aphanitic, dark gray to black igneous rock with a fine-grained, rough texture. The individual crystals are too small to be seen with the unaided eye, showing an opaque appearance and a dull to sub-vitreous luster.
Physical Characteristics
Dark gray to black body color with a light gray to white streak. It has an uneven to sub-conchoidal fracture, no distinct cleavage, specific gravity around 2.8 to 3.0, and high tenacity, making it extremely durable and brittle.
Optical Properties
Opaque in hand specimen; under microscopic thin-section analysis, it exhibits constituents that are doubly refractive with low birefringence depending on the mineral grains (plagioclase, pyroxene, olivine).
Hardness & Durability
Origin Region
Found globally in oceanic crust, volcanic islands, and continental flood basalt provinces (e.g., Deccan Traps, Columbia River Basalt Group)
Hardness & Durability
Mohs hardness typically ranges from 6 to 7 for constituent minerals, with high overall toughness and resistance to weathering, making it durable for construction and industrial use.
Care & Maintenance
Requires no special maintenance; extremely stable against heat, light, and household chemicals.
Rarity & Value
Very common; one of the most abundant rock types on Earth and planetary bodies, low monetary value unless of specialized scientific interest.
Special Characteristics
Often exhibits vesicular texture from trapped gas bubbles during cooling, sometimes filled with secondary minerals like zeolites, quartz, or calcite to form amygdaloidal basalt.
Lore & History
Historically used by ancient civilizations for ground stone tools, millstones, and monumental architecture due to its hardness and durability. In modern metaphysical practices, basalt (often in the form of hot stones for massage) is associated with grounding, endurance, and absorbing negative energy, though these are cultural traditions rather than scientific claims.