The Diamond is generally conceded to be the most beautiful as it is the most important of precious stones. While other stones at times exceed it in value, weight for weight, in total importance as an article of commerce other gems are hardly to be compared with it. Out of thirteen and one-half millions of dollars’ worth of precious stones imported into the United States in 1900, twelve million dollars’ worth were Diamonds. Not all this amount was employed for jewelry, since there is a large utilization of the stone for industrial purposes, but even for jewelry the Diamond has a largely preponderating use. Its points of superiority are its hardness, high refractive powers and hence play of colors, its transparency and its luster. In all these qualities it excels any other known mineral. Hence when in addition to these it exhibits different body colors, as is sometimes the case, no other gem can equal it in value. Usually the Diamond is colorless or white, although shades of yellow are also common. It is also known in shades of red, green and blue and in brown and black. The two latter are rarely transparent and grade into the varieties known as bort and carbonado, which have no value as gems but are highly important for industrial purposes. In composition the Diamond is pure carbon, thus not differing chemically from graphite or such forms of carbon as lamp-black, bone-black, etc. It is crystallized, but this can be said of graphite as well. Why carbon should assume the form of Diamond in one case and graphite in another, as well as being amorphous in other occurrences, is not known. Such behavior of a substance is known as dimorphism, and numerous illustrations of it are to be found in Nature. Being pure carbon, Diamond can be burned in the air. The finely divided dust can be burned in the ordinary blow-pipe flame, and for stones of ordinary size a temperature of about 900° C is sufficient. The possibility of consuming the Diamond by heat is said first to have been suggested by Sir Isaac Newton, who reasoned from the high refractive index of the stone that it was “an unctuous substance coagulated,” and hence probably combustible. Following this suggestion two Italians, Averani and Targioni, succeeded in 1695 in burning some Diamonds in a furnace, and since then the experiment has been repeated many times. The Diamond does not fuse in burning, but after becoming heated to redness gradually grows smaller, emitting sparks, till it entirely disappears. It leaves no ash except in the case of the impure form known as carbonado. The gas given off has been collected and analyzed and found to be carbon dioxide just as would result from the combustion of other forms of carbon. If protected from the air or free oxygen, the Diamond can be exposed to high heat without change.