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.
Background Silicon is the second-most abundant element in the earth's crust, after oxygen. It binds to oxygen, forming crystalline or amorphous silica (silicon dioxide, SiO2), silicic acid (Si(OH)4), and silicates, such as quartz.Silicon is present in rocks, soil, sand, and dust as crystalline silica.Silicic acid is formed naturally from silica and is readily absorbed in the human gastrointestinal tract.t binds to oxygen, forming crystalline or amorphous silica (silicon dioxide, SiO2), silicic acid (Si(OH)4), and silicates, such as quartz. Silicon is present in rocks, soil, sand, and dust as crystalline silica. Silicic acid is formed naturally from silica and is readily absorbed in the human gastrointestinal tract.