Lichen-Covered Basalt Boulder
Basalt with Epilithic Crustose Lichen · Mineral Specimen / Geologic Formation
Crystal System
Monoclinic and Triclinic (for constituent feldspars and pyroxenes within the rock matrix); amorphous for glass
Mineral Group
Silicates (Igneous rock composed of multiple mineral groups)
Chemical Formula
Complex silicate rock (Plagioclase, Pyroxene, Olivine) with organic lichen compounds
Formation Process
Igneous extrusion and cooling of mafic lava, subsequently exposed to weathering and biological colonization by crustose and foliose lichens over decades to centuries
About This Crystal
A weathered, dark gray to brownish-black igneous rock surface densely populated by patches of crustose lichens. The dominant lichen species show vibrant bright orange and muted grayish-white to greenish-white thalli tightly adhering to the rock face, following micro-fractures and contours of the stone
Physical Characteristics
Rock matrix is aphanitic to fine-grained with a dull, earthy to sub-vitreous luster. Streak is white to gray. Fracture is uneven to conchoidal. Specific gravity ranges from 2.8 to 3.0. Tenacity of the rock is brittle, while the covering lichen is leathery and dry
Optical Properties
Opaque rock matrix with non-reflective, matte to earthy surfaces; lichens display diffuse surface reflection with distinct pigmentation ranging from bright xanthoria orange to pale gray
Hardness & Durability
Origin Region
Found globally in volcanic regions, outcroppings, and glacial erratics, with specific colonization depending on local microclimates and atmospheric purity
Hardness & Durability
Rock matrix has a Mohs hardness of approximately 5 to 6; lichen crust is extremely soft and easily abraded. High durability against weathering due to the protective symbiotic crust
Care & Maintenance
Requires natural outdoor environmental conditions; if kept as a specimen, protect from indoor chemical pollutants, heavy scrubbing, and lack of ambient moisture/light which can kill the living lichen
Rarity & Value
Common in nature, highly variable in aesthetic appeal as a natural specimen, generally holds value as a teaching or landscape specimen rather than a commercial gem
Special Characteristics
Displays biological weathering and symbiotic colonization; lichens serve as natural bioindicators of air quality and environmental health
Lore & History
Representing the primal union of the mineral kingdom and biological life (fungus and algae symbiosis), lichens are often associated in earth-based philosophies with resilience, endurance, time passing, and the slow, steady transformation of barren rock into fertile soil