The 49th Annual Denver Gem & Mineral Show®
About the Exhibits in 2005
by Mr. Cenk Ozerdem
Department of Geosciences
Virginia Polytechnic Institute & State University
Quartz occurs in a large number of varieties, depending on its home environment.
When people think of quartz the standard hexagonal crystal comes to mind. However quartz crystals can be large (macrocrystalline) or small (microcrystalline); clear or any color of the rainbow; and can occur in all three geologic environments.
Gemstone qualities of quartz are most often found in volcanic environments. However, collectors used to believe that transparent quartz crystals were petrified ice.
The many different colors of quartz are the result of different elements such as ferric oxide (Amethyst), manganese (Rose Quartz), and even natural radioactivity (Smoky Quartz).
Quartz's physical properties, especially its hardness, means it can resist degradation and disintegration at high temperatures and pressures that other minerals cannot.
Many metamorphic rocks like gneiss, schist and quartzite contain large amount of quartz.
Quartz is common in creating fossils through a process known as silicification. This is when microcrystalline quartz crystallizes in pores in bone, wood or shell turning the remains into rock.
The quartz content of sandstones is important to geologists, as it tells the maturity of the rock. Quartz can make up to 60-70% of the grains found in sandstones, but the most common sandstones are made of over 95% quartz grains.