Quartz

There is more information available on this subject at Quartz on the English Wikipedia.

Quartz (from German "Quarz") is the most abundant mineral in the Earth's continental crust. It is made up of a lattice of silica (SiO2) tetrahedra. Quartz has a hardness of 7 on the Mohs scale and a density of 2.65 g/cm³.

Quartz belongs to the rhombohedral crystal system. The ideal crystal shape is a six-sided prism terminating with six-sided pyramids at each end. In nature quartz crystals are often twinned, distorted, or so intergrown with adjacent crystals of quartz or other minerals as to only show part of this shape, or to lack obvious crystal faces altogether and appear massive. Well-formed crystals typically form in a 'bed' that has unconstrained growth into a void, but because the crystals must be attached at the other end to a matrix, only one termination pyramid is present. A quartz geode is such a situation where the void is approximately spherical in shape, lined with a bed of crystals pointing inward.

Pure quartz is colorless or white, colored varieties include rose quartz, amethyst, smoky quartz, milky quartz, and others. Quartz goes by an array of different names. The most important distinction between types of quartz is that of macrocrystalline (individual crystals visible to the unaided eye) and the microcrystalline or cryptocrystalline varieties (aggregates of crystals visible only under high magnification). Chalcedony is a generic term for cryptocrystalline quartz. The cryptocrystalline varieties are either translucent or mostly opaque, while the transparent varieties tend to be macrocrystalline.

Although many of the varietal names historically arose from the color of the mineral, current scientific naming schemes refer primarily to the microstructure of the mineral. Color is a secondary identifier for the cryptocrystalline minerals, although it is a primary identifier for the macrocrystalline varieties. This does not always hold true.

Major Varieties

Chalcedony	Any cryptocrystalline quartz, although generally only used for white or lightly colored material. Otherwise more specific names are used.
Agate	Multi-coloured, banded chalcedony, semi-translucent to translucent
Onyx	Agate where the bands are straight, parallel and consistent in size.
Jasper	Opaque chalcedony, typically red to brown
Aventurine	Translucent chalcedony with small inclusions (usually mica) that shimmer.
Tiger's eye	Fibrous gold to red-brown coloured quartz, exhibiting chatoyancy].
Rock crystal	Clear, colorless
Amethyst	Purple, transparent
Citrine	Yellow to reddish orange to brown, greenish yellow
Prasiolite	Mint green, transparent
Rose quartz	Pink, translucent, may display asterism
Rutilated quartz	Contains acicular (needles) inclusions of rutile
Milk quartz	White, translucent to opaque, may display diasterism
Smoky quartz	Brown to grey, opaque
Morion	Dark-brown, opaque
Carnelian	Reddish orange chalcedony, translucent

As reported on in ENGCORP Field Report A79052, quartz is found on the planet Onyx.

A pink quartz monolith was on display at the Côte d'Azur Museum of Natural History on Sigma Octanus IV. Upon first engaging two Hunters in the room, SPARTAN Blue Team used Shredder Rounds to blow the floor under the Hunters' feet. When the Hunters fell to the floor below, John-117, Kelly-087, Frederic-104, and James-005 pushed the quartz monolith onto the Hunters, pinning them.

List of appearances

• Halo: The Fall of Reach (First appearance)
• Halo: Ghosts of Onyx