Vesicular Basalt with Coralline Algae Encrustations
Basalt (Aphanitic Mafic Igneous Rock) with Lithothamnion sp. · Mineral Specimen / Igneous Rock
Crystal System
Amorphous to Microcrystalline (Aphanitic texture) with an irregular, vesicular habit
Mineral Group
Silicates (Plagioclase Feldspar and Pyroxene rich)
Chemical Formula
Mainly SiO2 (~45–52%), MgO, FeO, and CaO with CaCO3 (encrustations)
Formation Process
Igneous: Volcanic extrusion where rapid cooling of lava traps gas bubbles (vesicles), later submerged or subjected to tidal splash allowing for biogenic carbonate growth
About This Crystal
A dark, dull, opaque volcanic rock characterized by a pitted (vesicular) surface. The specimen features irregular patches of pink, white, and pale green encrustations consisting of dried coralline algae and mineral deposits.
Physical Characteristics
Color: Dark grey to black; Streak: Grey; Cleavage: None; Fracture: Uneven; Specific Gravity: 2.8–3.0; Luster: Dull/Earthy; Fluorescence: Generally none.
Optical Properties
Opaque; No refractive index measurable via standard gemstone methods; No pleochroism or dispersion
Hardness & Durability
Origin Region
Common in volcanic coastal regions such as Hawaii, Iceland, and various oceanic islands
Hardness & Durability
Mohs Hardness: 5–6; High toughness for the base rock, though vesicular structures can be brittle. Surface encrustations are soft (Mohs 3).
Care & Maintenance
Wash with soft brush and plain water; avoid acidic cleaners which will dissolve the pink carbonate encrustations; store in a dry environment to prevent further degradation of biological matter.
Rarity & Value
Common; Value is minimal, primarily of interest as a geological or beach-found specimen. Commercial value is decorative or educational.
Special Characteristics
Vesicular texture (pitted appearance from volcanic gas); presence of marine biogenic encrustations providing a bi-colored pink and white surface contrast.
Lore & History
Basalt is historically used for grinding stones and construction. Metaphysically, it is associated with the Root Chakra and believed to provide grounding and strength during times of transition.