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Roger Weller, geology instructor            regional geology  planetary  gems

by Jason Jarvis
Physical Geology
Spring 2008

 Quartz, More Quartz and...Even More Quartz !

Quartz is a hard crystalline mineral which can be found in huge amounts on earth. It has many varieties of forms. It is a silicon dioxide, or SiO2. It is most common, and it makes up about 12% of the earth’s crust, volume wise. The name “quartz” comes from the German word “quarz,” which is originally of Slavic origin. Quartz crystals are rotary polar and have the ability to rotate the plane of polarization of light passing through them. They are also highly piezoelectric, which means that they become polarized with a negative charge on one end and a positive charge on the other when subjected to pressure. They will vibrate if an alternating electric current is applied to them. Ordinary quartz is shown in the picture below; the varieties will be discussed at a later point.

I.     Uses of quartz

          Quartz is used in many different ways. The most common uses are for glass, but also for electrical components, such as watches and pieces for
your computer. Obviously it also is a gemstone, usually one of its varieties is used, and quartz is also used for optical lenses.
         Chalcedony, another variety of quartz, can be used to make beads, cameos, and distinctive rings.

 Clear crystalline quartz is often cut into faceted gemstones to ornament necklaces, rings, and bracelets.

In manufacturing, quartz is used as an electrical component, to manufacture specialized tools, lenses, and laboratory glassware.

Sandstone is used in building, as is granite, and most people interact with something containing quartz at least once a day, since the mineral is so prevalent in daily life.

         Also, Quartz played a major role in World War II, in which the circuits of the radios used to communicate enemy fortifications, also included quartz. This makes quartz one of the most important minerals to win the war

II.   Varieties of quartz

Well known varieties of quartz include, but are not limited to:
         Amethyst, which is the purple gemstone variety.

         Then there is citrine, which is a yellow to orange gemstone variety of quartz, but very rare in nature, it usually is created by heating up Amethyst.

         Rock crystal is the clear variety of quartz, as shown in the above picture, and can also be used as a gemstone, yet is most likely to be used for one of the above mentioned uses.

         Lastly, Rose quartz, which is a pink to reddish pink variety of quartz.

         Please understand that not all the varieties are mentioned, since there are many more.

          But, not all varieties of quartz are naturally occurring. Prasiolite for example, is produced through heating, and even though citrine occurs naturally, it is so rare that most of it is also produced by heating amethyst.  

III.  Occurrence

Quartz usually occurs in hydrothermal veins or pegmatites. Quartz is a very common part of granite, sandstone and limestone, but many other materials could be included.

IV. History

Roman naturalist Pliny the elder believed quartz to be water ice, permanently frozen after great lengths of time. (The word "crystal" comes from the
Greek word for ice.) He supported this idea by saying that quartz is found near glaciers in the Alps, but not on volcanic mountains, and that large quartz crystals were fashioned into spheres to cool the hands. He also knew of the ability of quartz to split light into a spectrum. This idea persisted until at least the 1600s.

Later, Nicolas Steno discovered that no matter which way one distorts a quartz crystal, the long prism faces will always form a 60 degree angle.

Jacques and Pierre Curie, in 1880 were the first to discover the piezoelectric properties of quartz, yet the first quartz oscillator wasn’t invented until 1921, by a man called Walter Guyton Cady.


V.      References

For further information, see: