Lab Created Gems

Labs created gems are artificial gems which can look like natural ones, but they can be purchased at lower prices and of course experts can recognize that they are not authentic. You will find out for example how diamond is changed into graphite, at low temperature. This change is exothermal and the inverse transformation must be favored according to Le Chatelier principle, at high temperature. According to this principle as well, graphite change into diamond must be favored by pressure because diamond has a higher density, therefore a lower volume at the same mass than graphite. Many trials to manufacture synthetic diamonds, performed during a century have failed.

Since 1955 synthetic diamonds are manufactured industrially, by heating graphite at about 3000° and 125 000 atmospheres. The change speed is increased by little supplements of Cr, Fe or Pt. The catalyze role apparently consists in forming a film of melted metal on the graphite surface. Under these conditions the metal dissolves carbon and precipitates it as diamond, less soluble. There are obtained black diamonds of 0.02-0.05 g, which are used on industrial purposes.

A recent good procedure to obtain diamonds is based on a different principle: methane is used, at a lower pressure than the atmospheric one over diamond powder with the size of 1 micron, heated to 1000°. The little diamond crystals serve as crystallizing centers; A part of the carbon resulted by decomposing methane is deposed on the surface of these crystals whose network is thus extended in space; another part of the carbon is deposed as graphite. Graphite is removed by heating with hydrogen at 50 atmospheres, because it can be hydrogenated more quickly than the diamond.

Synthetic gems are also appreciated for their beauty and their durability. The value of a gem depends in general on four characteristics: the beauty of the stone; its rarity; its weight (karate, one karat = 0.2g) and resistance; and the skill with which the stone was cut and finished.

Properties: The crystalline structure of the diamond reflects all its properties. The high vaporization temperature, almost 4000° and the lack of a liquid phase are explained by the fact that while passing from crystalline state to vapors state covalence must be broken. At the high temperature of vaporization, carbon vapors are made of free atoms.
In the diamond crystal, atoms are maintained in their balance positions by forces which are much stronger than in metals or ionic crystals.

Optical properties of the diamond are as well in concordance with its crystalline structure. The total transparence (lack of absorption) reported to the visible and ultraviolet light proves that the electrons of the C-C links from the diamond can’t be excited by the frequencies of these electromagnetic radiations.

Diamond is less reactive than black coal and even than graphite. It is on fire, in molecular oxygen only at 800° C. By long heating at 1500°, in the absence of oxygen diamond is changed into graphite.

Gems like diamonds, rubies and emeralds represent one of the greatest financial supplies of the world. During wars or financial crises a lot of people used to change their money in gems, as they could be transported and liquidated more easily.

In the lab there can be produced sapphires having a perfect quality and of almost unlimited size.