Freestanding Quartz Terminated Point
This terminated quartz crystal is transparent and virtually inclusion-free. It was cut and polished in Brazil.
This type of quartz is also known as rock crystal. This name, which has been in use since at least the 17th century, refers to the transparent, colourless variety of quartz.
As glassmaking techniques improved in early modern Europe, high-quality colourless glass became known as crystal glass because of its resemblance to rock crystal.
Because of the shape of this quartz crystal, it acts as a prism. Therefore, when light passes through it at just the right angle, it can disperse white light into its component colours.
To see this, hold the crystal horizontally towards natural daylight (or your computer screen). Bring it close to your eye and rotate it very slowly. As you look slightly downwards, you'll see a spectrum of colours.
To the human eye, white light, such as natural daylight, appears colourless but is actually made up of all the colours of the visible spectrum combined.
