Spherulite
Image: <a href="//commons.wikimedia.org/w/index.php?title=User:Koltovoi&action=edit&redlink=1" class="new" title="User:Koltovoi (page does not exist)">Koltovoi</a> (CC BY-SA 4.0)
Mineral NameSpherulite
Chemical Formula(K,Na)AlSi3O8
Mohs Hardness6
Crystal Systemmonoclinic
Lustervitreous
Streak Colorwhite
CleavageGood in two directions at ~90 degrees
Fractureuneven
Specific Gravity2.55
Colorswhite, gray, pink
Transparencytranslucent
Mineral GroupTectosilicates
Usesscientific study, collector
Associated Mineralsquartz, biotite, hornblende
Raritycommon
Description
This image displays a microscopic view of a spherulite, characterized by its radiating, fibrous crystal growth pattern emanating from a central point. The white and blueish tones are likely interference colors observed under polarized light microscopy.
Geological Context
Spherulites commonly form in viscous felsic volcanic rocks like rhyolite and obsidian during rapid cooling, where crystals grow outwards from a nucleation point. They can also occur in some sedimentary rocks or as aggregates of other minerals, often composed of feldspar or chalcedony.
