Formula: CaMgSi2O6 Monoclinic
Diopside occurs in moderate to high-grade metamorphic rocks. It is particularly common in marbles, calc-silicate rocks, and amphibolites.
FLORENCE COUNTY: Found with tremolite in marble from a drill core into a metasedimentary sequence from the Bass Lake area, T.38N R.17E (Nielsen, 1984). Nielsen (1986) reports it occurs in several spots around the northwestern margin of the Dunbar Dome.
KENOSHA COUNTY: Chrome diopside occurs as a heavy mineral found in cores from a subsurface, diamond-bearing lamproite diatreme, discovered within the outskirts of Kenosha. (Carlson and Adams, 1997.).
MARATHON COUNTY: Diopside occurs in calcite veins cutting serpentine in a road cut in the middle of the north edge of Sec. 34 T.30N. R.6E. (Brown, 1995, personal communication)
ONEIDA COUNTY: Diopside occurs with scapolite, tremolite, grossular and calcite in veins in the intensely altered volcanic rocks at the Pelican River massive sulfide deposit in Sec. 29 T.36N R.9E, east of Rhinelander (Bowden, 1978). – Found in metamorphosed calc-silicate rocks at the Lynn massive sulfide deposit where it is associated with garnet and tremolite (Kennedy et al., 1991).