|Quartz is an important rock forming material and can develop under many different environmental conditions. Because of it's hardness and beautiful variety of forms, it is used widely as gemstone material.|
Included in this family is ;|
rock crystal (transparent, colorless, pure crytalline form);
amethyst (purple, caused by trace elements of iron);
rose quartz ( pink, rose red, caused by trace amounts of manganese or titanium);
citrine (clear yellow, caused by inclusions of colloidal iron hydrates);
smoky quartz (pale brown to black, caused by long term exposure to radiation);
milky quartz (milk white caused by micoscopic gas bubbles);
aventurine (glistening from enclosed scales of mica or hematite); and
tigereye (lusterous yellow, red, brown, or blue parallel fibers).
Quartz can form six-sided crystals but is more commonly found in masses. Quartz varies in colour depending on trace elements and the environment in which it was formed.
Under special conditions, if quartz is allowed to cool slowly, large crystals may form.
White, milky or snow quartz has microscopic gas bubbles which scatters light giving the quartz its milking appearance. Rock crystal is more rare, as it formed without gas bubbles leaving it "crystal clear". Amethyst, Ontario's official mineral, gets its violet or purple colour from trace elements of iron. Often, amethyst crystals have a coating of iron oxide also known as hematite. Tigereye quartz formed orginally as serpentine (a form of asbestos). Over time, heat and pressure caused the asbestos to change into the much harder quartz. The orginal fiber structure is retained giving the tigereye it's shimmering luster. This process is known as pseudomorphous. Iron or magnesium from the orginal serpentine gives the tigereye its distinctive colours of brown, red or blue.
Besides being valued for their beauty, quartz has important scientific and industrial uses. Quartz crystals are strongly piezoelectric, meaning their electrical properties change with pressure. A small electric current can cause a crystal to vibrate at a consistent frequency which is useful for clocks and other electronic devices such as radios. The piezoelectric effect also makes quartz crystals very useful as pressure sensors.