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.
Silica (quartz) Silica, SiO 2, is a white or colorless crystalline compound found mainly as quartz, sand, flint, and many other minerals. Silica is an important ingredient to manufacture a wide variety of materials. Quartz; Quartz is the most abundant silica mineral. Pure Quartz is colorless and transparent.