The best way to identify crystal is to take the piece to an appraiser or to look for a manufacturer marking. Find these marks at the bottom of the crystal piece.
If you are taking the crystal piece to an appraiser, it is best to send along prints or digital images of the pieces before showing the appraiser the actual piece. Some appraisers like to begin the process by looking over these photos before seeing the piece. It is also possible for individuals to view examples of distinguishing features of crystal pieces on some appraiser websites. As an alternative, an individual can visit a public library or bookstore to look at reference guides that show these identifying features.
In most cases, the manufacturer's mark is on the bottom of the stem of each crystal piece. Most crystal has an etching, sticker or symbol that serves as the marker. If the symbol is difficult to see, an individual may want to shine a light on the bottom of the stem to make it easier to see. Using a magnifying glass may also help to make the emblem more visible. Before buying new antique crystal, experts also recommend that individuals learn some of the most well-known markers, especially from manufacturers such as Lenox and Fostoria.
Isometric crystals are cube-shaped. Many diamonds are cube-shaped and are preferred for faceting, or cutting. Variations include the octahedron, a type of an elongated cube that is also prime cutting material.
Tetragonal crystals are rectangular, and feature two sides of equal length. An example is apophyllite. Golden topaz is an example of an orthorhombic shape, which is similar to the tetragon but with all sides having different lengths. Gypsum is monoclinic, an elongated rectangle with slanted ends that are perpendicular to one another.
Orthoclase has triclinic crystals, which are shaped like an elongated cube with no perpendicular sides. Triclinic crystals usually have four or five sides. Sapphire crystals are hexagonal, with six elongated symmetrical sides and two smaller perpendicular ends.
Gemstone cutting is called faceting. It is done on a machine that allows the operator to calculate precise angles. Before beginning, the cutter analyzes the crystal for shape, possible fractures and inclusions. Diamonds, for example, are most often cut into brilliant rounds because of their cubic shapes. Less of the diamond crystal is lost in the cutting process, producing a larger, flashier and more valuable gemstone.