Quartz

Category  :  Oxide mineral
Hardness  :  7 - lower in impure varieties
Gravity  :  2.65 constant; variable in impure varieties
Reflection  :  1.55 / 1.54
Color  :  Clear (if no impurities); also see Varieties
Chemical formula  :  SiO2
Crystal system  :  rhombohedral
Major varieties  :  Amethyst, Citrine Quartz, Rose Quartz, Colourless Quartz Or Rock Crystal, Cat’s Eye, Tiger’s Eye, Hawk’s Eye, And Bull’s Eye, Quartz, Chalcedony, Aventurine

Quartz is an essential constituent of granite and other felsic igneous rocks. It is very common in sedimentary rocks such as sandstone and shale and is also present in variable amounts as an accessory mineral in most carbonate rocks. It is also a common constituent of schist, gneiss, quartzite and other metamorphic rocks. Because of its resistance to weathering it is very common in stream sediments and in residual soils.

Quartz occurs in hydrothermal veins as gangue along with ore minerals. Large crystals of quartz are found in pegmatites. Well-formed crystals may reach several meters in length and weigh hundreds of kilograms.

Amethyst

The typical color is a rich, violet-purple, often distributed in patches or bands. It is given both oval and drop mixed cuts, step cuts, and other types of cuts used for colored stones. Amethyst normally has good luster and transparency. When the stones contain inclusions, a series of discontinuous, wavy parallel lines, visible with a lens, indicates that they are certain amethyst.

Citrine Quartz

Citrine is a variety of quartz whose color ranges from a pale yellow to brown. It is nearly impossible to tell cut citrine from yellow topaz visibly. Citrine has ferric impurities, and is rarely found naturally. Most commercial citrine is in fact artificially heated amethyst or smoky quartz. Brazil is the leading producer of citrine, with much of its production coming from the state of Rio Grande do Sul.

Rose Quartz

Rose quartz is a type of quartz which exhibits a pale pink to rose red hue. The color is usually considered as due to trace amounts of titanium, iron, or manganese, in the massive material. Some rose quartz contains microscopic rutile needles which produces an asterism in transmitted light. Recent X-ray diffraction studies suggest that the color is due to thin microscopic fibers of possibly dumortierite within the massive quartz.

Colourless Quartz Or Rock Crystal

Quartz is an essential constituent of granite and other felsic igneous rocks. It is very common in sedimentary rocks such as sandstone and shale and is also present in variable amounts as an accessory mineral in most carbonate rocks. It is also a common constituent of schist, gneiss, quartzite and other metamorphic rocks. Because of its resistance to weathering it is very common in stream sediments and in residual soils.

Cat’s Eye, Tiger’s Eye, Hawk’s Eye, And Bull’s Eye Quartz

:It consists (in its original form) of two pairs of reflective glass spheres set into a white rubber dome, mounted in a cast iron housing. This is the kind that marks the centre of the road, with one pair of cat's eye showing in each direction. A single-ended form has become widely used in other colours at road margins and as lane dividers. Cat's eyes are particularly valuable in fog and are largely resistant to damage from snow ploughs.

Chalcedony

This is the name given to the microcrystalline varieties of quartz that form concretionary deposits. The typical color is blue whitish-gray, but for ornament purposes, the types that have been variously colored by small quantities of other elements are usually used. All varieties are cut into cabochons, engraved, or made into seal stones or rounded, polished and pierced for necklaces and other items of jewellery.

Aventurine

It is actually a metamorphic rock, a quartzite, containing platelike crystals of other minerals, usually green mica. It is improperly called Indian jade. It is normally not transparent, but somewhat turbid. It is generally cut into curved pieces for necklaces or other jewels. Because of its heterogeneous structure, it does not easily acquire a good polish. It is much more brittle than jade.

Our Location Map

Location map