Rock Crystal

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Rock Crystal (Colorless Quartz)
Chemical composition SiO2 Silicon dioxide
Crystal system Trigonal
Habit Prismatic
Cleavage Poor
Fracture Conchoidal
Hardness 7
Optic nature Uniaxial +
Refractive index 1.544 - 1.553
Birefringence 0.009
Dispersion Low, 0.013
Specific gravity 2.65
Lustre Vitreous
Pleochroism None
Quartz crystals from the personal collection of Barbra Voltaire

Rock Crystal is the common name for colorless quartz. The material is abundant and has been used for centuries as a gem. Quartz crystals are among the earliest talismans. Examples of rock crystal objects date back to 75,000BC. Every culture on the planet has attributed magical power to quartz crystals. The Ancient Greeks prized rock crystal and believed it to be water frozen by the gods to a state of perpetual solidity. They carved the material into seals and intaglios. The Japanese considered it "the perfect jewel", symbolizing patience and perseverance, the infinity of space and purity. Native Americans used quartz crystals as a hunting talisman and "fed" them with deer's blood.

70mm Crystal Ball

Crystal balls were brought to Europe from the Near East by the Crusaders. They were credited with the ability to cure diseases. In Scotland and Ireland, farmers used crystal balls to keep livestock healthy. Today, crystal balls are still used for mystical divination, gazing and New Age healing. They vary in size ranging from small beads measuring a few millimeters in diameter to the largest known crystal ball in existence. It is displayed at the Smithsonian Institution in Washington, D.C. It is called the "Warner Crystal Ball." This specimen has a weight of 48.5 kilograms and a diameter of 32.5 centimeters.

Inclusions in Quartz: Click on Image for full Size

Acicular inclusions in quartz, possibly rutile.
Photo courtesy of Conny Forsberg
Doubly terminated Quartz crystal in quartz. Often referred to as Herkimer Diamond, it is actually a location and habit specific variety of colorless quartz.
Photo courtesy of James Swisher