Instrument data from three buoys in Lake Superior provide a reliable record of water temperatures since about 1980, and the information also shows that, with water temperatures running in the mid-to-upper 60s (and even warmer closer to shore), âwe are at record temperatures for this time of year,â according to Austin.
The talc is formed by the alteration of sedimentary magnesium carbonate rocks (dolomite and magnesite) at elevated temperature and pressure below the earth's surface. While the magnesium is fixed in situ, the silica is transported by silica-containing hot fluids to react with the Magnesium- bearing carbonates to form talc. These altered rocks are then talc-rich dolomites or magnesites. This type of deposits usually deliver the massive talcs accompanied by carbonates, chlorite and some quartz.
talc Talc is the softest mineral; it can be easily scratched with you fingernail. It may have a pearly luster. Talc is often described as having a greasy or soapy feel to it. Talc is commonly white, but can also be a pale green or pale pink. You might get talc and gypsum confused because they can have similar appearances. 12. gypsum Gypsum is a soft, light-colored mineral. Its color can be colorless and transparent (selenite) or white, pale pink or pale brown. If crystallized, it displays one direction of excellent cleavage, but the cleavage fragments are much thicker than those of mica and the fragments are not elastic. Generally, it lacks the greasy feel of talc.