MILKY QUARTZ, the cloudy white variety of quartz
- VARIETY OF: Quartz
, SiO2 , Silicon Dioxide.
- USES: Ornamental stone.
- COLOR: various shades of white, usually milky.
- INDEX OF REFRACTION: 1.544-1.553
- BIREFRINGENCE: 0.009
- HARDNESS: 7
- CLEAVAGE: none
- CRYSTAL SYSTEM: trigonal
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.
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
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.
A Quartz Phantom
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),
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.
is a general term for several microscopic quartz varieties.