GEMINI 



3460 



GEMSBOK 



facets sloping to the flat culet. This 

 method, by assisting refraction and 

 reflection, is especially adapted for 

 showing off the beauties of dia- 

 monds and rubies. A half-brilliant 

 is only faceted from girdle to table, 

 having a flat base. (2) Roses are 

 rather like the half-brilliant, the 

 top suj^aee being cut with six or 

 more triangular facets of equal size, 

 with flat back. These styles are use- 

 ful for small, thin stones. (3) Brio- 

 lettes are pear-shaped, covered 

 with triangular facets, but without 

 table, girdle, or culet. They are 

 sometimes drilled across, to be 

 worn as swinging pendants. 



(4) Star cut stones were fashion- 

 able early in the 19th century ; 

 they are combinations of the bril- 

 liant and rose, with facets grouped 

 in multiples of six. (5) Step or trap 

 cut stones may be of any shape, 

 though very often nearly rect- 

 angular. The facets are long and 

 flat, placed parallel to the girdle. It 

 is an excellent style for making the 

 most of colour effect. ( 6 ) Table cut 

 stones are either four-sided double 

 pyramids or regular octahedra, 

 with large table, table and culet 

 either equal or varying in size. 



Gemmation. A. Piece ot sponge laden 

 i, spicules of buds directed away from 

 k, spicules of parent directed towards 

 B. Bud which has been set free and has 

 the extremity 



From The Cambridge Natural History, M 



(7) The dome-shaped cabochon is 

 one of the oldest styles. A cabochon 

 may be more or less convex, the 

 convexity being equal or dissimilar 

 on both faces, or the base may be 

 flat. The treatment will depend 

 upon the nature and quality of the 

 stone. This form of dressing is ap- 

 plied more particularly to opaque 

 and translucent stones, such as tur- 

 quoise and opal, but it is also used 

 for deep-toned garnets and a few 

 other coloured stones. Bastard cut 

 stones are those of mixed styles. 



The great art of gem cutting is 

 to bring out the special beauty of 

 individual specimens, removing or 

 minimising blemishes, with as little 

 loss to the bulk of the stone as pos- 

 sible. Emeralds are nearly always 

 cut square or oblong, with step 

 facets. Diamonds are the most diffi- 

 cult stones to cut and polish, owing 

 to their extreme hardness and brit- 

 tieness. Yet the gem cutters' appli- 



ances are quite 



simple. The rough 



dressing of dia- 

 monds and a few 



other gem stones 



may begin with 



cleaving or slitting 



removing a 



defective or 



awkwardly shaped 



part ; the stone 



being cemented on 



a wooden holder, 



with the line of 



cleavage parallel 



to the stick. Then 



a sharp, thin, steel 



blade is placed 



against the stone 



and struck sharply with a mallet, 



clean cleavage taking place. The 



operation can also be performed by 



sawing with a thin steel disk, but 



this often results in loss of brilliancy, 



even to the development of icy 



flakes, tiny fissures only visible to 



the eye as slight cloudiness. 



Facets are formed by grinding 



against a steel revolving cone or 



cutting with the steel disk. The 



cone and disk of diamonds must be 



thinly coated with a paste of dia- 

 mond dust and 

 * olive oil. This 

 ^ paste, or a paste 



of emery powder 

 ' in water, is used 

 for other stones. 

 Polishing is ac- 

 .1 complished by 

 N^ 1 ar^ < these pastes in a 



finer form, or with 

 tripolite, rotten - 

 stone, or jewellers' 

 rouge. Boring is 

 performed by the 

 rapid rotation of a 

 diamond point. 

 All these tools are 



worked on a lathe. 



Engraving, both incised carving 



(intaglio) and relief carving (cameo), 



is carried out by means of small 



steel wheels at the end of a rotating 



axis in a lathe. Certain of the softer 



stones, such as rock crystal, agates. 



and other siliceous 



stones, are etched 



with hydrofluoric > 



or other suitable 



acid instead of 



being carved. The 



surface is covered 



with wax, into 



which the design i;- 



cut with a graver, 



down to the stone. 



which is then 



washed with acid. 



When the wax is 



removed the de- 

 sign will be found 



etched in the 



stone. 



with buds a-i ; 

 their free ends ; 

 the osculum, j. 

 become fixed by 



ac mill an & Co. 



Gemmi Pass. One of the gorges in the Bernese Alps 

 threaded by a mule track 



Gemini OR THE TWINS. One of 

 the ancient Ptolemaic constella- 

 tions. Castor and Pollux form the 

 heads of the Twins. Their feet 

 stand on the Milky Way. 



Gemmation (Lat. gemmare, to 

 bud). Biological term signifying 

 both the process of budding and 

 the arrangement of buds on a 

 stalk. More particularly, the term 

 is restricted to the asexual method 

 of reproduction in certain lowly 

 organisms in which the offspring 

 take their origin as an outgrowth 

 or bud from the parent, afterwards 

 becoming separated as an in- 

 dividual. See Botany. 



Gemmi. Pass or mule-track 

 over the Bernese Alps, Switzerland. 

 It communicates between Frutigen 

 in Berne, and Leukerbad in the can- 

 ton of Valais, and reaches an alt. 

 of 7,640 ft. The track passes the 

 Dauben See, and is often called 

 the Daube Pass. There is an hotel 

 on the summit, and from it there is 

 a remarkable view, including the 

 Matterhorn, Monte Rosa, the Dent 

 Blanche, and the Wildstrubel. 



Gemsbok (Oryx gazella). Spe- 

 cies of antelope, found in the desert 

 regions of S.W. Africa. It is 

 remarkable for its long straight 

 horns, which sometimes reach a 

 length of 45 ins. The animal is 

 about 4 ft. high, and is grey on the 

 back and sides, with white below. 



Gemsbok, the long-horned antelope found in South- 

 West Africa 



