UC-NRLF B 14

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26 GEMS AND PRECIOUS STONES. If the star corundum is blue it is a star-sapphire, if red a star-ruby, and so on. Star-sapphires are very plentiful in the New England district of this Colony, although usually of too dark colour for cutting purposes. These gems are best cut en caboclion, care being taken to get the centre of the star in the middle of the convex surface. It is only of late years that these star stones have come into fashion in Europe. Not many years ago they could have been purchased in Ceylon for small sums, but star rubies at the present time, if of good quality, fetch high prices ; being rare they are highly prized. In the Hope collection there were six asterias of a very high character. Of course, the value of these gems is determined by their size and quality. Star sapphires range from 2 to 100 ; star rubies are still more valuable. Besides the ornamental uses to which these gems are put, there is that of the more important one in connection with manufacture. That this item of from the fact that consumption is not an insignificant one, may be judged in the United States of America, where the watch industry is of great magnitude, the consumption of gems alone for the jewelled works of the watches manufactured in that country, cannot be less than 12,000,000 annually, of which nearly half are rubies and sapphires, the remainder being principally garnets. The consumption, too, of "bort," used in the drilling and working of these gems, reaches many thousand carats per annum. It is, of course, not necessary that these gems be of large size, but it is important that they be free from flaws, of the correct hardness. good colour, transparent, and of In the New England district of this Colony, sapphires are plentiful, and although, unfortunately, many are very dark and opaque, yet very many bright, clear gems may be gathered of good colour, transparent, and correct hardness. Many of these transparent corundums, too, are of a green colour (inferior Oriental emeralds), and these should not be discarded. As the greater part of the gems used in America for watch-making purposes are imported, and the whole of those used in England, the collection of these gems is a matter worthy of some consideration. Simple Forms of the Hexagonal System. As all the varieties of corundum crystallize in the hexagonal system, it will be as well to consider the most simple of the forms belonging to it. In this system (unlike all the others) there are four axes ; one, the principal, has no fixed length, the remaining three lie at right angles to the principal axis in one plane, and they are inclined to each other at an angle at 60 degrees. This plane, by joining the three axes, forms a hexagon, these axes being all the same length. The primary form of this system is the hexagonal pyramid (two six-sided pyramids placed base to base), all the other forms being derived from it. In this form the principal axis joins the two six-sided solid angles (refer to the cubical system in the article diamond for the meaning of terms), the lateral axes joining the lateral solid angles if belonging to the first order, and the centre of the lateral edges if belonging to the second order. (These orders are only of importance in combinations.) It has twelve faces, these being isosceles triangles, and they are acute or obtuse as the principal axis is or short. This is a common form of the corundum. long
HEXAGONAL SYSTEM. /Simple forms. Hexagonal Pyramid. Prbsm. jfyramid
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GEMS AND PRECIOUS STONES. 71 lolite
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GEMS AND PEECIOUS STONES. 73 Malach
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FORMS OF CUTTING PRECIOUS STONES rt
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76 GEMS AND PEE CIO US STONES. Ther
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GEMS AND PRECIOUS STONES. Mode of B
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Abbas Mirza diamond Adamantine spar
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Diamond reduced by cutting 74 split
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Opal, hardness of historical Hondur
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PAGE. Vaal River Diamond Fields val
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U.C. BERKELEY LIBRARIES
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UC-NRLF B 14

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