Quartz exists in more than 100 varieties and in many colors and degrees of translucence. Quartz comes in "massive" and "crystal" forms. A crystal of quartz is generally opaque, while a massive piece is usually clear. Quartz crystals have definitive characteristics that set them apart from massive quartz and from the crystals of other minerals.
Instructions
1. Look for geometric shape characteristics. Massive minerals have no geometric shape and resemble rocks. The crystal form of a mineral has the same molecular structure as its massive form, but the molecules are arranged in a specific structure that gives the crystal a distinct geometric shape. Some clear quartz will have a flat surface, but if there are no other flat faces, the mineral is in its massive form and not crystallized.
2. Amethyst is one of many varieties of quartz crystals.
Examine the structure of the crystal shape. Crystals are six-sided prisms. The faces are rarely symmetrical. The crystals terminate on one or both ends in a deep rhombohedral pyramid, having three larger and three smaller faces. Crystals can be either short and stocky or elongated and slender. You may need to do some testing to properly identify certain crystals.
3. Check the crystal for striations. In quartz, striation lines will run across the crystal parallel to the cap. You can easily see these lines in large crystals, but they can be faint in smaller crystals, and you will need a magnifying glass to see them.
4. Test for hardness if you are unsure of the crystal identity. "Hardness" does not indicate that the crystal will not shatter if it is struck. Rather, minerals can only be scratched by harder minerals. Quartz can only be scratched by topaz, corundum and diamond.
Scratch the mineral gently in a spot that won't spoil the value of the crystal using a piece of quartz or a 7 hardness pick. If it scratches, the mineral is not quartz. Repeat the process with a topaz or an 8 pick. Quartz will scratch.
Tags: geometric shape, massive form, only scratched