The famous spinel in the Royal Crown of England, once thought to hare been a ruby, was known to the Black Prince ; it came into his possession, and was afterwards worn by Henry V at Agincourt; it is thus of some historic importance, although its intrinsic value has become lessened by its real composition having been discovered. The knowledge that so many of the historic rubies are simply spinels, casts grave doubts as to whether many other large stones still supposed to be rubies are not spinels.
To illustrate the necessity of correct nomenclature in reference to these gems, the recent history of a fine blue spinel is worth repeating. It was an Indian-cut stone, forwarded to London from that country as a sapphire; it was reeut in London and sold as a sapphire ; it was subsequently found to be a spinel, and was returned by the purchaser to the merchant from whom he bought it. This stone weighed after recutting 25 carats. Mr. Streeter mentions two fine spinels that were exhibited in the London Exhibition of 1802, one of perfect colour and free from flaws weighed 197 carats ; when reeut in London it weighed 81 carats, and was then a " perfect stone." The other weighed 102-1/2 carats and when reeut weighed 72-1/2 carats.
Most of the large spinels come from India, certainly from the East, and one of the finest recorded belonged to the King of Oude; it was of the size of a pigeon's egg, and had great lustre. Besides India, spinels fit for jewellery come from Burmah, Siam, Ceylon, and the United States of America.
The red varieties of the spinel known as "spinelruby" and "balas ruby" have little to distinguish them; the stones bearing the latter name are inferior in colour and brilliancy to the former, and less like the true ruby. The origin of the term "balas" has become quite a debatable question; many theories have been put forward by different writers, but it is unnecessary to notice them ; it is sufficient that the name distinguishes the stone.
The Persians have a tradition that the mines from which these gems are obtained were discovered through the mountain being divided by an earthquake, and that they were mistaken for the true rubies. There are famous mines at Badakhshan in Tartary, where balas rubies are found, and the natives of this district have a superstition that two large stones always lie near each other, and when one is found they most diligently search for the other; and it is stated that, if unable to find it, they will even break the stone found in order to keep up the belief.
The natives of India call the spinel Lai Kumani, and ascribe to it valuable medicinal properties.
Spinels occur embedded in granular limestone, and with calcite in serpentine, gneiss, and allied rocks. It is also found in the cavities of masses ejected from some volcauoes, for instance, the ancient ejected masses of Mount Somma. They also largely occur as water-worn pebbles in the beds of rivers, and alluvial deposits of many localities. A few good stones of small size have been found in California. A pale blue spinel is found in Sweden, embedded in limestone. Green spinels are found in slate in the Ural Mountains. In Bohemia small rose-red crystals occur with pyrites.
Spinel, as has been stated, crystallizes in the cubical system, and its principal form is the octahedron, sometimes showing faces of the rhombic dodecahedron, it is also found as twins, the twinning taking place parallel to one face of the octahedron. Some of the small crystals are so perfect, and of such a good lustre, that they might be used for the purpose of ornamentation in their natural state. Their form of crystallization readily distinguishes them from the ruby ; the other differences have already been pointed out.
Eroni garnets, they may be distinguished by being infusible, garnets fusing easily in thin splinters in the blowpipe flame. Both these minerals crystallizing in the cubical system, their optical properties cannot be used to dis-