Quartz is one of the most common minerals in the Earth’s crust. As a mineral name, quartz refers to a specific chemical compound (silicon dioxide, or silica, SiO2), having a specific crystalline form (hexagonal). It is found is all forms of rock: igneous, metamorphic and sedimentary.

Iron (element #26, symbol Fe) is the most common metallic element in the universe. When pure it is a dark, silvery-gray metal. It is a very reactive element and oxidizes (rusts) very easily. The reds, oranges and yellows seen in some soils and on rocks are probably iron oxides.

Tungsten (W) is a gray-white metallic element that is stable and is very resistant to acids and bases. Tungsten has the highest melting temperature of any metal (3422 ° C or 6192 ° F), and the second-highest of all elements (carbon is highest).

Tin is one of the earliest metals known and used. Because of its hardening effect on copper, tin was used in bronze implements as early as 3,500 B.C., although the pure metal was not used until about 600 B.C.

Chromium (Cr) is a hard, bluish metallic element. The only ore of chromium is the mineral chromite and 99 percent of the world’s chromite is found in southern Africa and Zimbabwe. Geologists estimate that there are about 11 billion tons of mineable chromite ore in the world, enough to supply the current demand for hundreds of years.

Lead (element #82, symbol Pb) is a very soft, blue-gray, metallic element. It is primarily produced from the mineral galena. It has been used since antiquity.