Dark green crystal group of greenalite from Kyoto Prefecture, Honshu Island, Japan. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Greenalite
An iron serpentine-group mineral — a green iron silicate of banded iron formations.
Intro adapted from Wikipedia (CC BY-SA).
Greenalite is an IMA-recognized mineral species in the silicate class, with the chemical formula (Fe²⁺,Fe³⁺)₂₋₃Si₂O₅(OH)₄.
It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Serpentine, Clay structural group.
Key properties: specific gravity 2.85–3.15; optically isotropic.
IMA symbol Gre, grandfathered status — known before the IMA’s founding, named in 1903.
A primary phase in some banded iron formations.
It is found associated with Minnesotaite, stilpnomelane, siderite, chamosite, quartz, pyrite.
In allusion to its green color.