Chamosite, a member of the chlorite group, is relatively rare at Mont Saint-Hilaire.
Color ranges from brown to dark-green.
Luster is vitreous to silky, greasy or dull. Diaphaneity is translucent to opaque. Crystal Habits include spherical aggregates and micaceous plates to 15mm across. Streak is greenish-white to white. Associated Minerals include albite, anatase, calcite, catapleiite, dolomite, fluorapatite, gmelinite, pyrite, quartz, rutile, siderite and sphalerite.