WGNHS
Wisconsin Geological and Natural History Survey

Anthophyllite

Root-beer brown elongated anthophyllite crystals with pink pyrope garnet and white quartz. Field of view is about 1.7 cm left to right. Skunk Creek, Tobacco Root Mountains, near Sheridan, Madison County, Montana. (Image by W. S. Cordua.)

Formula: (Mg,Fe)7Si8O22(OH)2 Orthorhombic

Description:

Anthophyllite is a mineral formed from the metamorphism of magnesium-rich rocks. It is often associated with other amphibole minerals, pyrope, and cordierite.

JACKSON COUNTY: Anthophyllite occurs as long radiating fibrous crystals and masses intergrown with talc at the Jackson County Iron Mine, Sec. 15 T.21N R.3W near Black River Falls. Associated minerals are chlorite, biotite, magnetite, pyrite, cummingtonite and actinolite (Jones, 1978).

MARINETTE COUNTY: Anthophyllite is noted by Cummings (1978) in rocks associated with sulfide zones in the Quinnessec. Formation in T.36N R.18E. It is reported from the Duval massive sulfide body, Sec. 2 and 3 T.35N R.18E and Sec. 28 T.36N R.18E (Hollister and Cummings, 1982).

RUSK COUNTY: Anthophyllite occurs as “sheaf-like bundles of radiating needles” in a mineralized iron formation in the Eisenbrey massive sulfide deposit north of Ladysmith (NW sec. 17 T.35N. R.6W. (May, 1996).

WOOD COUNTY: Massive sheets of anthophyllite occur with talc and serpentine at the Milladore talc deposits (Milwaukee County Public Museum specimen).