Andradite
Image: <bdi><a href="https://www.wikidata.org/wiki/Q56247090" class="extiw" title="d:Q56247090"><span title="mineral collector and dealer">Robert M. Lavinsky</span></a></bdi> (CC BY-SA 3.0)
Mineral NameAndradite
Chemical FormulaCa3Fe2(SiO4)3
Mohs Hardness6.5
Lustervitreous
Streak Colorwhite
Cleavagenone
Fractureconchoidal
Specific Gravity3.85
Colorsreddish-brown, brown, black, yellow, green
Transparencytranslucent
Type LocalityFranklin, New Jersey, USA
Mineral GroupSilicates
Usescollector, gemstone
Associated Mineralsgahnite, calcite, pyroxene
Rarityuncommon
Description
This specimen displays numerous reddish-brown andradite garnet crystals, some with a vitreous luster, embedded within a dark greenish matrix. Lighter calcite and darker gahnite/pyroxene crystals are also visible, creating a complex mineral assemblage.
Geological Context
Andradite typically forms in contact metamorphic rocks, especially skarns, and in some igneous rocks. The Franklin, New Jersey locality is renowned for its unique and complex mineral assemblages, formed under high-grade metamorphism of zinc-rich carbonate rocks.
