Minerals

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.

Hornblende is a inosilicate amphibole minerals, which are two type hornblende minerals. They are ferrohornblende and magnesiohornblende. They are an isomorphous mixture of three molecules; a calcium-iron-magnesium silicate, an aluminium-iron-magnesium silicate, and an iron-magnesium silicate.

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...

Plagioclase is series of framework silicate minerals in feldspar group. Plagioclase is a continuous series of solid solutions known as the plagioclase feldspar series,...

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,

A light mica, lepidolite is Earth’s most common lithium-bearing mineral. Its name is derived from two Greek words: lepidos, which means “scale,” and lithos, which means “stone.” Although typically pale lilac, specimens can also be colorless, violet, pale yellow, or gray. Lepidolite crystals may appear pseudohexagonal. The mineral is also found as botryoidal or kidneylike masses and fine- to coarse-grained, interlocking plates. Its perfect cleavage yields thin, flexible sheets. Lepidolite occurs in granitic pegmatites, where it is associated with other lithium minerals, such as beryl and topaz. The mineral is economically important as a major source of lithium, which is used to make glass and enamels. It is also a major source of the rare alkali metals rubidium and cesium.

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 most common pyroxene, augite is named after the Greek word augites, which means “brightness”—a reference to its occasional shiny appearance. Most augite has a dull, dark green, brown, or black finish. Augite occurs chiefly as short, thick, prismatic crystals with a square or octagonal cross section and sometimes as large, cleavable masses. It occurs in a solid-solution series in which diopside and hedenbergite are the end-members. Augite is common in silica-poor rocks and various other dark-colored igneous rocks, as well as igneous rocks of intermediate silica content. It also occurs in some metamorphic rocks formed at high temperatures (1,065°F/575°C or above). Augite is a common constituent of lunar basalts and some meteorites. Notable crystal localities are in Germany, the Czech Republic, Italy, Russia, Japan, Mexico, Canada, and USA. Because it is difficult to distinguish between augite, diopside, and hedenbergite in hand specimens, all pyroxenes are often identified as augite.