STANDING TALL: PLAINS INDIANS ENJOYED HEIGHT, HEALTH ADVANTAGE. COLUMBUS, Ohio - Equestrian Indian tribes on the American Plains in the late 1800s were the tallest people in the world, suggesting that they were surprisingly well-nourished given disease and their lifestyle, a new study found.
Limestone often contains variable amounts of silica in the form of chert (chalcedony, flint, jasper, etc.) or siliceous skeletal fragment (sponge spicules, diatoms, radiolarians), and varying amounts of clay, silt and sand (terrestrial detritus) carried in by rivers.
Pure limestone is made of calcium carbonate. Limestone often contains variable amounts of silica in the form of chert or flint, as well as varying amounts of clay, silt and sand as disseminations, nodules, or layers within the rock.The primary source of the calcite in limestone is most commonly marine organisms.These organisms secrete shells that settle out of the water column and are deposited on ocean floors as pelagic ooze or alternatively is conglomerated in a coral reef (see lysocline for information on calcite dissolution).ere, it decays and becomes a part of the rock known as limestone. So, limestone is made of decayed calcium, or calcite.   +++   Almost-but a chemical element cannot decay! The primary mineral of this sedimentary rock is calcite, calcium carbonate, which is a chemical compund (CaCO3).