The ruby is one of the most valuable gemstones in the world, prized for its brilliant red color and rarity. It is also one of the most imitated, with stones such as tourmaline and garnet as well as colored silica glass being marketed and sold as rubies. A real ruby is a variety of the mineral corundum, or crystalline aluminum oxide, which turned red from a slight chromium impurity in the crystal structure. Several key characteristics related to its structure may help you to determine the difference between a simulated ruby and a real ruby.
Corundum, and therefore the ruby, is one of the hardest minerals on Earth. It is ranked nine out of 10 on the Mohs scale which measures the hardness of minerals, and is second only to the diamond. Like a diamond, the surface of a real ruby is difficult to scratch. Simulated rubies, including those made from glass or stones like garnets, fall much lower on the Mohs scale.
Simulated rubies are often less dense in appearance than real rubies. Rubies come from deposits deep in the earth, many of which can be found in Asia, particularly Myanmar, Vietnam, Thailand and Afghanistan as well as the African nations of Tanzania and Kenya. The ruby crystals are formed slowly in a high temperature environment like many other mineral rocks. As a result, real rubies are not perfectly clear, but rather have a natural, dense appearance.
Inclusions are flaws or irregularities that occur in gemstones and can be used to differentiate a real ruby from a simulated ruby. Inclusions are the result of pieces of foreign matter or small mineral deposits being trapped while the stone was forming. A ruby's inclusions could be compared with human fingerprints — they are unique to each individual stone and provide proof that it was formed by nature and is therefore genuine.
Scientific study is another way to determine whether a ruby is real or simulated. While less popular with the general public, methods such as chemical analysis and observation through a microscope may be used by experts to spot a synthetic ruby — that is, one that was created in a lab. Chemical analysis will detect impurities, such as the presence of lead, that are not present in natural rubies. Observation with a microscope will determine the presence and location of the stone's curved growth features.