Garrelsite, NaBa3Si2B7O16(OH)4

Garrelsite, NaBa₃Si₂B₇O₁₆(OH)₄, originally described in 1955, has recently been reexamined by Charles Milton and Adolf Pabst and by Subrata Ghose and Horst H. Ulbrich. The latter have reanalyzed the mineral and determined the structure; the powder pattern is indexed on the basis of their 1972 cell constants. These were refined in 1973 to ɑ=14.639 A, b=8.466 A, c=13.438 A, β=114.21°, space group C2/c. Garrelsite has been found in two drill cores penetrating the Green River Formation (Eocene) at two localities in Uintah County, Utah, and in the borate deposits of the Kramer district, Kern County, Calif. The original description of the morphology has been corrected, and the optical orientation has been redetermined.