Bigcreekite

Description

Bigcreekite, ideally BaSi2O5·4H2O, is a newly identified mineral species that occurs along very thin transverse fractures in fairly well-laminated quartz-rich sanbornite portions of the rock.
Bigcreekite is biaxial negative, with indices of refraction h1=1.537(2), h2= 1.538(2), h3= 1.541(2); X = b, Y =a, Z = c and 2V_[submeas]= 59.2° , 2V_{[sub calc]}= 60.1°. The crystal structure of bigcreekite was solved as space group Pnma, with cell parameters a = 5.038? , b = 9.024 ? , c = 18.321 ? , and Z = 4.

Physical properties

Bigcreekite is a hydrous chain silicate containing four-membered rings which form chains of silica tetrahedra, parallel to [100] and staggered in the [001] direction. Water molecules fill the large spaces between the rows of silicon tetrahedra.