Grunerite from the Shinyama ore deposit, Kamaishi mine, Japan.

Most of the clinopyroxene in the clinopyroxene skarn containing the 4D copper orebody of the Shinyama deposit was altered to Ca-amphibole and cummingtonite-grunerite owing to late-stage T decrease. Microprobe analyses indicate that most of the amphibole is cummingtonite-grunerite, generally considered rare in skarns, and that the Mg/(Mg + Fe) mole fractions of Ca-amphibole and cummingtonite-grunerite are 0.24-0.38 and 0.27-0.33, respectively. A zonal arrangement is observed from limestone to igneous rock: cummingtonite-grunerite skarn, Ca-amphibole skarn, (clinopyroxene skarn) and garnet skarn. This zonal arrangement is attributed to the increase of XCO₂ towards the limestone.-L.C.C.