The Timmins Talc-Magnesite deposit is a hydrothermally altered ultramafic rock composed, at its core, largely of talc and magnesite although, at its fringes, the content of calcium in the carbonate increases.
The deposit under consideration has long been viewed as a potential source of magnesite and talc. These minerals are found in a variety of deposit types throughout the world and have a variety of end uses.
The best known of the minerals directly and widely exploited for its magnesia content is magnesite (MgCO3), one of the calcite group of rhombohedral carbonates, which includes calcite (CaCO3), siderite (Fe2CO3) and rhodocrosite (MnCO3), among others.
Although the genesis of natural magnesite deposits can be complex, it is distinguished in nature in two distinct physical forms, namely crystalline, (with a wide range of visible crystal sizes) and cryptocrystalline, sometimes referred to as amorphous, where the crystal size is not detectable to the eye and will range from 1 to 10 micrometers. The two types not only differ in crystal structure but in the sizes of the deposits and modes of formations.
Large-scale talc deposits form when magnesium in magnesium-rich rocks reacts with hydrothermal silica in the final phases of regional or contact metamorphism. Most commonly, talc (Mg3Si4O10(OH2)) or steatite (the massive and fine grained form of talc) replaces serpentine in an ultramafic rock like peridotite, either completely or m ........
