CLINOCHLORE White Crystals to 3Mm Occurred on the 7Th Level 2+ (Mg,Fe )5Al(Si3al)O10(OH)8 North at the Osceola Mine (A

“collyrite” = kaolinite). 3. Osceola mine, Calumet: Aggregates of hollow pseudohexagonal CLINOCHLORE white crystals to 3mm occurred on the 7th level 2+ (Mg,Fe )5Al(Si3Al)O10(OH)8 north at the Osceola mine (A. E. Seaman Mineral A common member of the chlorite group found in Museum collection, Michigan Technological low grade metamorphic terrains and as an University). Energy dispersion X-ray spectra of alteration product of mafic minerals; forms a solid this material show it is essentially end-member solution series with its Fe2+ analog, chamosite clinochlore. (q.v.). Much of the “clinochlore” replacing garnet Keweenaw County: 1. Moore and Beger from the Republic and Michigamme iron districts (1963) indicate that “pennine” is the most cited in the literature is probably chamosite (e.g., abundant chlorite in altered copper lode rocks. 2. Dorr and Eschman, 1970; Morris, 1983). South of Eagle Harbor: A chlorite in drill core EH- “Pennine,” “ripidolite,” and “prochlorite” are 1-1357, analyzed by Jolly and Smith (1972), yielded obsolete synonyms. Northern Peninsula. a composition corresponding to ferroan aluminian Dickinson County: Jensen quarry at Randville: clinochlore admixed with a smectite group Occurs locally in the Randville Dolomite at contact mineral. 3. Mandan mine: As small, gray-green, with aplite dikes (Conrad, 1952). pseudotrigonal crystals intergrown with saponite, lining cavities in brecciated prehnite. 4. Clark Gratiot County: Near Ithaca, T10N, R2W in mine: As yellow-gray microcrystals (D. Behnke, Michigan Basin Deep Drill Hole in both altered personal communication, 1991). basalt-gabbro units as replacement of olivine, interstitial glass, and possibly some clinopyroxene. Marquette County: Marquette and Sands Also in veinlets cutting lower unit basalt: chlorite- quadrangles: “Prochlorite” is reported as a actinolite and serpentine-chlorite-epidote (Heinrich constituent of the Mona Schist (metabasalt) (Gair and Pollack, 1978). Chlorites from the lower unit and Thaden, 1968). have been analyzed (McCallister et al., 1978) and FROM: Robinson, G.W., 2004 Mineralogy of found to be ferroan clinochlore. From X-ray Michigan by E.W. Heinrich updated and diffraction data Stakes (1978) determined a similar revised: published by A.E. Seaman Mineral composition with a IIb polytype. Museum, Houghton, MI, 252p. UPDATE Gogebic County: NW ¼ section 5, T45N, R39W: As rosettes to 1 cm in veins in gneiss (M. Heilman, personal communication, 2009). UPDATE FROM: Robinson, G.W., and Carlson, S.M., 2013, Mineralogy of Michigan Update: published online by A.E. Seaman Mineral Museum, Houghton, MI, 46p.

Figure 59: Clinochlore crystals from the Clark mine, near Copper Harbor, Keweenaw County. Crystals are approximately 1 mm across. Dan Behnke specimen and photograph.

Houghton County: 1. Hancock mine: In base of amygdules (Moore and Beger, 1963). 2. Isle Royale mine: Gray-white pseudohexagonal crystals and masses (the latter sometimes mislabelled as