Tochilinite (approximately FeS(Mg,Fe)(OH)2) is locally abundant in Hole 1068A serpentinites from Cores 173-1068A-21R and 22R. It occurs in veins, as fillings in void space, and in intergrowths with serpentine and andradite. An apparently related mineral, but with Ca and Al largely replacing Mg, occurs in association with, and possibly as a replacement of, pyrrhotite in serpentinite breccias from the bottom of Core 173-1068A-20R. The transition from Mg-Fe-rich brucite tochilinites to Ca- and S-rich carbonate tochilinites is consistent with increasing sulfur and oxygen activity upsection. Tochilinite has been reported at other sites on the Iberia Abyssal Plain and is abundant to the point of being a rock-forming mineral in several samples from Site 1068. Rather than being a mineralogical curiosity, tochilinite appears to be common and a major sink for sulfur in the upper serpentinites of the Iberia Abyssal Plain.

All Ni, Co, and Cu are assigned to sulphide.

Supplement to: Beard, James S (2000): Occurrence and composition of tochilinite and related minerals in Site 1068 serpentinites. In: Beslier, M-O; Whitmarsh, RB; Wallace, PJ; Girardeau, J (eds.) Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 173, 1-9