QUARTZ(MILKY)[GEM]

Listing description
Milky Quartz is any quartz crystal or cluster that is white in color and cloudy. The cloudy white character of the crystals is what lead to the variety name, milky. The cloudiness of milky quartz comes from microscopic inclusions of fluids that have been encased in the crystal from the time the crystal first grew.
Detailed description
From a cynical point of view the inclusions have ruined the crystal from being used for the many purposes that quartz crystals are tasked to do (e.g. gemstones or optic purposes). However, milky quartz is used in many fine ornamental carvings and the fluid inclusions can give milky quartz a attractive greasy luster unlike the other varieties of quartz.
Milky quartz is often responsible for the cloudy phantoms inside of otherwise clear rock quartz, amethyst, citrine or smoky quartz. The milky quartz may have formed at an early stage of the crystal's growth and a later stage of clear quartz growth covered the milky quartz. The effect results in seemingly a crystal within a crystal and the interior crystal may have a ghostly look, hence the name phantom. The milky quartz-amethyst phantom combination results in an ornamental stone called chevron amethyst. The bands of amethyst and milky quartz make thin well defined chevrons of purple and white that are attractive as polished stones and in ornamental carvings.
Milky quartz is occasionally associated with gold in hydrothermal veins. Prospectors searching for gold laden ore look for outcrops of milky white quartz veins. Many of the most beautiful gold specimens are the ones that have the lacy gold extruding from the pure white milky quartz. Other attractive associations with milky quartz include those with rhodochrosite (pictured above), fluorite, calcite, galena, pyrite, elbaite, micas and many many others.
Milky quartz is only one of several different quartz varieties. Other varieties that form macroscopic (large enough to see) crystals are as follows:

  • Amethyst is the purple gemstone variety.
  • Citrine is a yellow to orange gemstone variety that is rare in nature but is often created by heating Amethyst.
  • Prasiolite is a leek-green gemstone variety that is rare in nature but is created by heating Amethyst from certain locations.
  • Rock crystal is the clear variety that is also used as a gemstone.
  • Rose quartz is a pink to reddish pink variety.
  • Smoky quartz is the brown to gray variety.
Agate is a general term for several microscopic quartz varieties.
Quartz is the second most abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2.
There are many different varieties of quartz, several of which are semi-precious gemstones. Especially in Europe and the Middle East, varieties of quartz have been since antiquity the most commonly used minerals in the making of jewelry and hardstone carvings.
The word "quartz" is derived from the German word "quarz", which was imported from Middle High German, "twarc", which originated in Slavic (cf. Czech tvrdy ("hard"), Polish twardy ("hard"), Russian твёрдый ("hard")), from Old Bulgarian (Church Slavonic) тврьдъ ("firm"), from Proto-Slavic *tvьrdъ.[6]
Crystal habit
Quartz belongs to the trigonal 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.
At surface temperatures and pressures, quartz is the most stable form of silicon dioxide. Quartz will remain stable up to 573 °C at 1 kilobar of pressure. As the pressure increases the temperature at which quartz will lose stability also increases.
Above 1300 °C and at a pressure of approximately 35 kilobars, only β-quartz is stable. The latter is not the same as normal quartz (or α-quartz), low quartz or just quartz. β-quartz has higher symmetry, is less dense and has a slightly lower specific gravity. The conversion, from one solid substance to another solid substance, of quartz to β-quartz is quick, reversible and accompanied with a slight energy absorption. The conversion is so easily accomplished that when a crystal of quartz is heated to β-quartz, cooled back down, heated again to β-quartz, etc., the quartz will be the same as when it started.
The reason that the conversion is so easily accomplished is that the difference between quartz and β-quartz is relatively slight. The bonds between the oxygen and silicon atoms are "kinked" or bent in quartz and are not so "kinked" in β-quartz. At the higher temperatures the atoms move away from each other just enough to allow the bonds to unkink or straighten and produce the higher symmetry. As the temperature is lowered, the atoms close in on each other and the bonds must kink in order to be stable and this lowers the symmetry back down again.
Although all quartz at temperatures lower than 573 °C is low quartz, there are a few examples of crystals that obviously started out as β-quartz. Sometimes these are labeled as β-quartz but are actually examples of pseudomorphic or "falsely shaped" crystals more correctly labeled 'quartz after β-quartz'. These crystals are of higher symmetry than low quartz although low quartz can form similar crystals to them. They are composed of hexagonal dipyramids which are a pair of opposing six sided pyramids and the crystals lack prism faces. Quartz's typical termination is composed of two sets of three rhombic faces that can look like a six sided pyramid.
 (Microscopic) crystal structure
α-quartz crystallizes in the trigonal crystal system, space group P3121 and P3221 respectively. β-quartz belongs to the hexagonal system, space group P6221 and P6421, respectively.[7] These spacegroups are truly chiral (they each belong to the 11 enantiomorphous pairs). Both α-quartz and β-quartz are examples of chiral crystal structures composed of achiral building blocks (SiO4 tetrahedra in the present case). The transformation between α- and β-quartz only involves a comparatively minor rotation of the tetrahedra with respect to one another, without change in the way they are linked.

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