Quartz Crystals & Mineral Specimen


Quartz consists of mainly silica, or silicon dioxide (SiO2) and is one of the earth’s most abundant minerals behind feldspar.  It can be found all over the world (minable too) and can form at all temperatures! Due to the durability of this mineral, it can also be found in the tops of mountains and in numerous types of sand.  Quartz is a part of the trigonal crystal system with the ideal shape being in a six-sided prism with a six-sided pyramid at each end. Quartz can develop in two different forms, macrocrystaliine and cryptocrystalline (microcrystalline). Of the two, macrocrystaliine is more common and has large visible crystals or large intergrown crystals.  Cryptocrystalline quartz is dense, compact, and typically have microscopic crystals. Quartz crystals can be twinned, distorted or even intergrown with each other. Well-formed quartz crystals can be formed in a “bed” with one termination pyramid being visible. There can also be double terminated crystals which develop without an attachment.  Quartz can also form in a geode, which is a rock cavity filled with crystals. Quartz has different color varieties which include smoky quartz, rose quartz, and amethyst. There are also shape varietieswhich are scepter quartz, gwindel or quartzine.  

A couple of the more famous localities of fine crystalized quartz mineral specimens include the Ron Coleman Mines in Arkansas, and Arkansas in general produces some very fine quartz. You can find large, clear, and complex pieces here. 

Another notable source is in Santander, Colombia. They produce some very fine and gemmy clear complex quartz crystals. 

Other notable information on Quartz

  • Refractive index:  
  • Macrocrystalline = 1.54-1.55
      • Crypto = 1.53-1.54

    (refractive index or index of refraction of a material is a dimensionless number that describes how light propagates through that medium)

    • Specific gravity: 2.65

    (specific gravity is the ratio of the density of a substance to the density of a reference substance; equivalently, it is the ratio of the mass of a substance to the mass of a reference substance for the same given volume)

    • Moh’s scale: 7; but can be lower due to impurities within the mineral

    (scale of hardness running from 1 to 10 using a series of reference minerals; position on scale depends on the ability to scratch minerals rated lower)