Graphite is like diamond, graphite is a form of native carbon crystalline with its atoms arranged in a hexagonal structure. Graphite is opaque and dark gray to black. It occurs as hexagonal crystals, flexible sheets, scales, or large masses.
Arsenic is a native element with the formula As and atomic number 33. Known since antiquity, arsenic is widely distributed in nature, although it is unusual in native form. It is classified as a semimetal, because it possesses some properties of metals and some of nonmetals. Crystals are rare, but when found they are rhombohedral.
Sulfur is the tenth most common element by mass in the universe, and the fifth most common on Earth. It (also spelled sulphur) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent, and nonmetallic. Under normal conditions, atoms form cyclic octatomic molecules with a chemical formula S8.
Silver is an element with the chemical symbol Ag and atomic number 47. Opaque and bright silvery white with a slightly pink tint, it...
Gold has been the most prized metal that is a chemical element with the symbol Au. It is opaque, has a highly attractive metallic...
Antimony usually occurs in massive, leafy or granular form. It has a flaky texture that makes it shiny, silvery, bluish white and brittle. It occurs in rare, usually massive, leafy or granular form.
As a native metal, bismuth has been known since the Middle Ages. A German monk named Basil Valentine first described it in 1450. Bismuth is often found uncombined with other elements, forming indistinct crystals, often in parallel groupings. It is hard, brittle, and lustrous. It is also found in grains and as foliated masses. Silver-white, it usually has a reddish tinge that distinguishes it. Specimens may have an iridescent tarnish. Bismuth is found in hydrothermal veins and in pegmatites and is often associated with ores of tin, lead, or copper,
Five percent of Earth’s crust is made up of iron. Native iron is rare in the crust and is invariably alloyed with nickel. Low-nickel iron (up to 7.5 percent nickel) is called kamacite, and high-nickel iron (up to 50 percent nickel) is called taenite. Both crystallize in the cubic system. A third form of iron-nickel, mainly found in meteorites and crystallizing in the tetragonal system, is called tetrataenite. All three forms are generally found either as disseminated grains or as rounded masses. Kamacite is the major component of most iron meteorites. It is found in most chondritic meteorites, and occurs as microscopic grains in some lunar rocks. Taenite and tetrataenite are mainly found in meteorites, often intergrown with kamacite. Iron is also plentiful in the Sun and other stars.
The first documented discovery of platinum was by the Spaniards in the 1500s, in the alluvial gold mines of the Río Pinto, Colombia. They called it platina del Pinto, from platina, which means “little silver,” thinking that it was an impure ore of silver. It was not recognized as a distinct metal until 1735. It is opaque, silvery gray, and markedly dense. Platinum usually occurs as disseminated grains in ironand magnesium-rich igneous rocks and in quartz veins associated with hematite, chlorite, and pyrolusite. When rocks weather, the heavy platinum accumulates as grains and nuggets in the resulting placer deposits. Crystals are rare, but when found they are cubic. Most platinum for commercial use is recovered from primary deposits. Native platinum typically contains iron and metals such as palladium, iridium, and rhodium.
Copper was probably the first metal to be used by humans. Neolithic people are believed to have used as a substitute for stone by...
The hardest known mineral, diamond is pure carbon. Its crystals typically occur as octahedrons and cubes with rounded edges and slightly convex faces. Crystals may be transparent, translucent, or opaque. They range from colorless to black, with brown and yellow being the most common colors. Other forms include bort or boart (irregular or granular black diamond) and carbonado (microcrystalline masses).