From time to time, especially large diamonds have been found in different parts of the world, the largest being the Cullinan diamond, found at the Premier Diamond Mine of South Africa. It weighed 3025 carats or about a pound and a quarter, and was valued at over $3,000,000. It was presented to King Edward VII, who had it cut into 11 brilliants, four of which are larger than any other diamond yet found. Other famous diamonds, like the Kohinoor, 106 carats, found in India in 1304; the Regent, 136 carats, also found in India; the Orloff, 193 carats, set in the eye of an Indian idol; the South Star, 125 carats, the largest ever found in Brazil; the blue Hope, etc., have in many cases romantic and interesting stories woven about them.
Though for ages diamonds have been highly prized gems, it is only in comparatively recent times that cutting and polishing have been resorted to, for the purpose of enhancing their brilliancy. This is done by grinding reflecting faces on the original stone, by the aid of discs of iron or tin in which diamond dust has been embedded. Diamond chips and cloudy or imperfect diamonds are used for making tools for cutting glass, rock drills, etc.
Phosphorus
The element phosphorus at ordinary temperatures is an almost colorless, faintly yellow, solid substance of glistening appearance and waxy consistency. In Nature it does not occur pure, but always as one of its compounds. It is of great importance to man for it is one of the essentials for plant growth and also for the higher animals, being required for the bones and to some extent for nervous tissue. Originally it is found in all the igneous rocks. Some of the phosphorus is removed by solution and carried to other regions and to the sea. From this distribution it comes into the sedimentary rocks, and, when they are altered by heat, into the metamorphic rocks. Thus it has a wide, though by no means even, distribution. The soils formed by disintegration of these rocks probably all have some phosphorus in them; but where there is vigorous plant growth, it soon tends to become exhausted, and must be renewed. For this reason the use of phosphates has become of prime importance in Agriculture. The possession of beds of rock carrying phosphorus has come to be of international importance. The United States is particularly fortunate in this respect, and produces over 25% of the world’s supply of phosphates. Most all the phosphorus is recovered either from phosphate minerals, the most important of which is apatite, or from the non-crystalline and impure mixtures of phosphate minerals and other substances, discussed under phosphate rock.
[Apatite]
Ca₅F(PO₄)₃
[Pl. 49]
Occurs in crystals, concretionary nodules, or in bedded masses; hardness, 5; specific gravity, 3.2; color reddish-brown or green, rarely white or colorless; luster vitreous; translucent on thin edges.
Apatite occurs in hexagonal prisms, usually with the ends truncated by a basal plane, and with one or more sets of pyramidal faces between the prism and the basal plane. Crystals range in size from tiny to over a foot in diameter. There is but one cleavage and that is basal. The crystal form, cleavage, and hardness will easily determine this mineral. Apatite is usually associated with igneous or highly metamorphic rocks, such as granites, gneisses, and crystalline limestones. While the phosphoric acid of apatite is highly desirable for use in fertilizers, the crystals do not occur in sufficient abundance to make them commercially available, and non-crystalline phosphate rocks are resorted to for this purpose.
Crystals of apatite are found at Norwich and Bolton, Mass., Rossie and Edenville, N. Y., Suckasunny and Hurdstown, N. J., Leiperville, Penn., Wilmington, Del., etc. Templeton, Canada, is perhaps the best known locality for fine apatite.
[Turquois]
H₅[Al(OH)₂]Cu(OH)(PO₄)₄
Occurs in seams and incrustations; hardness, 6; specific gravity, 2.7; color bluish-green; streak blue; luster waxy; translucent to opaque on thin edges.