Tan crystal aggregates of the rare Ca-Al silicate mineral cebollite from the TL in Colorado (Gunnison County, Colorado, United States of America). Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY 4.0
Cebollite
Cebollite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ca₅Al₂(SiO₄)₃(OH)₄.
It is a member of the Melilite structural group.
Key properties: Mohs hardness 5; specific gravity 2.96; Dull luster; optically biaxial.
IMA symbol Cbl, IMA status: questionable, named in 1914.
An alteration product of melilite in a carbonatite (Iron Hill, Colorado, USA); along a diabase-chalk contact (Scawt Hill, Ireland); in zeolitized plagioclase-rich gneiss, amphibolite, and basalt xenoliths (Letseng-La-Terai kimberlite.
It is found associated with Melilite, natrolite, calcite, phlogopite, vesuvianite, garnet, diopside.
The name refers to Cebolla Creek, Colorado, in the drainage of which the mineral was first collected.