Andesite
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Mineral NameAndesite
Chemical FormulaVariable (intermediate silicate rock)
Mohs Hardness5
Streak ColorGreyish white
CleavageNot applicable (rock); constituent minerals have cleavage
FractureConchoidal to uneven
Specific Gravity2.5
Colorsgrey, white, black
TransparencyOpaque
Type LocalityNarcondam Island
Mineral GroupIgneous Rock
Usesconstruction aggregate, road material, dimension stone
Associated Mineralsfeldspar, hornblende, pyroxene, biotite
Raritycommon
Description
A rounded, light grey volcanic rock with visible white feldspar and black hornblende phenocrysts, giving it a speckled, porphyritic appearance.
Geological Context
Andesite forms from the rapid cooling of intermediate-composition lava, typically found in volcanic arcs above subduction zones and island arcs.
