Milky Quartz is a mineral with a hardness of 7 out of 10 on the Mohs scale of mineral hardness [?]. These Trigonally structured gems are made of silicon dioxide, their full chemical compound being SiO2.
Milky Quartz is a milky white translucent to opaque variety of crystalline quartz of somewhat greasy luster. It is the commonest variety found in pegmatites and hydrothermal veins. The color is generally caused by numerous bubbles of gas and liquid in the crystal.
The milky color is caused by small cavities filled with numerous small fluids and CO2 in liquid condition. It is used as a gemstone, and also called greasy quartz. When it contains minute particles of gold, it is named gold quartz. "Quartz en chemise" is a milky quartz but the milkiness is not deep.
White quartz (often called milky quartz) has profuse minute cavities containing water or liquid carbon dioxide. Much vein quartz is white quartz and this type is often gold-bearing. Such material with included gold grains has been cut as plates or cabochons, perhaps as souvenirs of the mining camps.
This mineral occurs commonly in igneous, metamorphic, and sedimentary rocks, and can be frequently found in mineral veins with metal ores.
Famous finds include a crystal weighing 13 metric tons from Siberia. Milky quartz is common in the Alps.
Varieties include Hyaline (opalescent milky quartz).
Where there are quartz crystals, there is gold, as it develops together in hydrothermal veins, so miners looking for gold-laden ore often seek outcrops of milky white quartz. But gold occurring with quartz is one of the world's rarest forms of natural gold and is found in only a few locations in the world.
Milky Quartz is used for jewellery and ornaments.
Quartz is used in glassmaking, ceramics, refractories, building materials, and abrasives. Its piezoelectric property makes it useful in pressure-sensitive devices. However, the cloudiness of milky quartz prevents it from being used in optical and electronic applications.