Feb. I, 1886.] THE TROPICAL AGRICULTURIST. 



589 



some of them are very good judges indeed, — supposed 

 to be a true oriental taby or red sapphire, but its 

 crystalliiie form — a regular octohedron— showed it to 

 be a spinel. 



He states that the dark-blue or blackisli v.iriety 

 of spinelle called ceylanite or pleonaste is ottered 

 for sale by the Shans under the same name as 

 sapphire. Gem sand containing small fragments of 

 garnet, beryl, and spinel, together with the more 

 precious stones, is a regular article of merchandise 

 with ihe Shaus, Three-fourths of the mass consists 

 of spinel. Purchasers may rest assured that the 

 valuable stones have, as a rule, been all removed 

 by the wily Shaus. 



Of couise, the ruby, sapphire and spinel mines of 

 Upper Burma belong now to the British Raj, 

 Streeter, in his notice of " precious spinel," states: — 

 Under the generic name Spinel several minerals 

 are included, as the Spinel Ruby, Balas Ruby, also 

 Pleonaste, or Ceylonite, Candite, and other less 

 valuable crystals. 



The precious Spinel is found either detached, or 

 embedded in granular limestone. It varies in colour, 

 presenting carmine, blue, rose-red, reddish-brown, or 

 some tinge of orange. It is fomid. loose in the 

 sand in Mysore and Hindostan, but in Burmah. 

 Pe*^^, Ceylon, Saffragam, and Matura it occurs in 

 well-formed, sharp-angled octahedra. In deep water- 

 courses, subject to irregular inundation, it occcure 

 accompanied with Zircon. Garuet, and magnetic iron 

 ore ; and in granite, accompanied with Apatite. 

 What is said of Mysore must be read in the light 

 of the scepticism of Mr. Ball of the Indian Geo- 

 logical Survey, and as to " Ceylon," with " Satfra- 

 gam " and •' Matura "added, as if they two latter were 

 countries separate from Ceylon, we are reminded of 

 the statement in all the books that graphite is 

 found in " Travancore, Ceylon." We quote the 

 further interesting information furnished by Streeter, 

 which shows that good, large crystals of spinel are 

 quite equal in value to sapphires. In view of what 

 Mr. Ball writes in his Geological Manual, however, 

 there can be little doubt that the specimens of blue 

 spinel referred to below, owed their origin to either 

 Burma or Ceylon : — 



In North Amex-ica, between Amity and Andover, 

 lome crystals of extraordinary magnitude have been 

 found, iiicasuring Iti inches in diameter, in com- 

 pany with granular limestone and SeiTieutine. 



Although its form, which has the octahedia for its 

 base, has caused it to be classed in the regular gem 

 system, yet it can be readily distinguished from the 

 Ruby, to which it has been allied, by its inferior 

 hardness, and its specific gravity, which varies from 

 35 to 38, and is in this respect similar to the Topaz. 

 A peculiarity of Spinel is that the light which is 

 reflected from the depth of the gem, no matter what 

 the colotu' of the stone, is always of a pale yellow. 

 The lustre is vitreous, and displays every degree of 

 transparency. The refraction is simple, and in no 

 stone is this more real and abiding than in this 

 species. It is rendered electric by friction, but not 

 by heat. 



Spinel is a combination of alumina and magnesia. 

 The varieties of color are due to the magnesia being 

 replaced partially by iron oxide (Fe.O), zinc oxide 

 (Zn.O), or manganese oxide (Mg.O), and lime (Ca.O) ; 

 and the alumina, by ferric oxide (Fe.O). 



One of the finest specimens of Blue Spinel, a 

 thickish oblong stone, was not long since in the 

 possession of Slessrs. Pittar, Liverson it Co. It was 

 an Indian-cut stone, weighing 'Ml carats. It was, 

 on its arrival, re-cut by ^Ir. .7. N. Forster, of Ijond<'ni 

 and weighed, after re-cutting, 25 carats. There is a 

 strange nistory attached to this stone ; it was con- 

 signed from India as a Sapphire; subsequently it 

 was found to be a Spinel, wlitreupon the purchaser 

 returned it to the merchant, who at once wrote to 

 the con.Kignor in India, but the statement was not 

 believed. The merchant determined to have it cut, 

 and afterwards sold- it for a much larger nnm than 

 it had been valued at aa a, Sapphire. 



In the Exhibition of 1862 there were two every 

 fine Spinels ; one from India was cut eit cabo hon, 

 forming an octagon-shaped stone, of perfect color and 

 free from tliws. It weighed 197 carats. This was 

 cut by Mr. .1. N. Forster to an iSl-carat "perfec- 

 tion stone." Tlie other Spinel was also an octagon- 

 .shaped stone, of perfect color, very "spread," and 

 free from flaws. It weighed 102^ carats, and was 

 re-ciit by Mr. Forster, and then weighed 72i carats . 

 It is strange that both these stones arrived fro m 

 India in the same year, viz., 18*>1. One specimen 

 obtained by Dr. Heron is said to have weighed 49 lb , 

 it is in three pieces, and contains cavities studded 

 with crystals of Corundum. 



In iVleronitz, in jiohemia, little rose-red crystaln 

 are found, in company witli Pyrites; also in the 

 Liebenhurgen, in gold sand. At Aker, in Sweden, 

 palo-blue and pale-grey varieties are found in lime- 

 stone. 



Crystals are found in the Ovens River, in Victoria, 

 and also in the pearl rivers of New South Wales, 

 and in other part of Australasia. 



The Blue Spinel is found in Sweden, Antwerp, 

 and Ceylon both loose and as imbedded crystals. 

 They are easily distinguished by ther foliated 

 fracture ; the color generally is a faint-blue, violet 

 indigo, or a seladine-green. It is translucent, and 

 contains 3 to 4 per cent of iron. 



Pleonaste was called Ceylonite, by Rome de I'lsle, 

 who analyzed it with a number of other crystals 

 brought from Ceylon. It was Hauy who, seeing its 

 crystals resembled that of the Spinel, desired to 

 give it a special position in the system of minerals 

 and named it Pleoiiasle, which signifies superfluity. 

 Further investigation showed that it was in reality 

 a black variety of the Spinel. This has the best 

 cleavage of the whole class; it is easy and parallel 

 to the faces of the octahedron. 



The specific gravity of this stone rises from 3'5 

 to 3"8. It cansists principally of alumina, and about 

 II) per cent of protoxide of iron. Its infusibility 

 before the blow-pipe, and its formation with borax 

 into an iron-colored glass, are the surest indications 

 of Pleonaste. Acids have but little influence upon 

 it. It is found in Russia and other cold climates, 

 but it is also found in Ceylon, as well as m the 

 Dolomite region in Ratana. 



Spinel, in consequence of its lustre, color aud 

 hardness, is used for personal ornament, and for 

 objects of luxury ; but it is only when the crystals 

 are fine and large that they are considered 

 gems. Ill cutting it receives the same form as the 

 Ruby. 



Spinel Ruby, called Balas Ruby, varieties in value 

 according to its cut and color. 



Ill the inventory of the French Crown .leweU, in 

 the year 1791, we find the following : — 



One Spinel Rnby of 561 carats .. *2,000 

 One „ 4 2-5th „ .. 12 



One „ 3| „ .. 12 



One Balas Ruby 20g „ .. 400 



One „ 12s „ .. 120 



At the present time small 



stones range from . . 5s to 10s a carat. 



Medinmstones, of fair color.. 20s to 40.s ,, 

 Largo stones . . . . 60s to lOOs „ 



Specimen stones attain even a higher value. 

 Balas, called Balais Ruby, are pale-red, or roae)^ 

 red gems, with a tinge of blue appearing at the 

 angles of the octahedron which gives them a milky 

 kind of shimmer and depreciates their value. The 

 color is due to chromic acid. 



The Balas Ruby varies much in price; for ex- 

 ample, a dark rose-red of 10 millimetres, square-cut 

 and polished as a Brilliant, pure and lustrous, will 

 sell for £12 while a pali-rose of like size will be 

 worth sixteen shillings only in value depends en- 

 tirely on the demand and the character of the 

 stone, occasionally a fine specimen of five carats 

 will realize il.50. 



From the article 'Burma,' iii the new edition of tlie 

 Kncyclopicdia lirilannico. we quote the (oUowjng 

 paragraph : — 



