THE GARNET GROUP 349 



The fact that garnet is singly refracting, prevents its being mistaken for other stones 

 which it may resemble in appearance, such, for example, as ruby or emerald, although this 

 character does not distinguish it from a glass imitation. The absence of dichroism in a 

 cubic mineral like garnet is, moreover, a further aid in its discrimination. The colour is the 

 same in ^vhatever direction light passes through the crystal, and the two images seen in the 

 dichroscope are absolutely identical in shade. The absence of dichroism is most useful in 

 distinguishing garnet from ruby. So similar in colour may the two stones be that even the 

 practised eye of an expert fails to discriminate between them. As we have already seen, the 

 garnet is frequently mistaken for ruby ; for example, on account of the similarity in colour 

 the fine red garnet associated with the diamond in South Africa is known as " Cape 

 ruby." 



As a rule, garnet fuses before the blowpipe with moderate ease ; a few varieties 

 fuse with more difficulty, and some are quite infusible. Crystallised garnet is unattacked 

 by acids, except hydrofluoric acid ; after fusion, however, the material does not resist their 

 action. The specific gravity of the mineral is also considerably less after fusion ; thus 

 the specific gravity of a yellowish-red calcium-aluminium garnet fell from 3"63 to 2"95. 

 The varieties richest in iron are the most easily fusible ; these, moreover, have a slight 

 action on the magnetic needle, and the mass which remains after fusion is attracted 

 by a magnet. All garnets when rubbed on cloth acquire a feeble charge of positive 

 electricity. 



The forms of cutting employed for garnet ai'e those best suited to more or less darkly 

 coloured stones. Most varieties are cut en cahochon, with a circular or oval outline, and 

 with a very considerable curvature, so that the stone is high and hemispherical in shape. In 

 the case of very dark specimens, the underside is hollowed out so as to render the stone 

 thinner and more transparent, a device adopted for scarcely any other precious stones. 

 These so-called garnet-shells (Plate IV., Fig. 176) have been found in numbers in Roman 

 ruins, so that the device was evidently known in ancient times. The table-cut and the 

 step-cut are the most usual forms, while the mixed-cut is not infrequently seen. With dark- 

 coloured stones each of these forms must be cut as thinly as possible. The table or large 

 facet at the front of the stone, instead of being plane frequently has a convex curvature. 

 The rosette or brilliant is used for some kinds of garnets and irregular, fanciful forms are 

 also met with. A few cut garnets are represented in Plate XIV., Figs. 4, 6, 8, and 10, and 

 in Plate XVIII., Fig. 7. Grains of garnet are often provided all round with small facets, 

 aiTanged regularly and systematically or in no particular order ; these are bored and strung 

 together for bi'acelets and necklaces. Stones of the lighter shades of colour are mounted 

 a jour, while the darker specimens are often mounted upon a burnished foil of silver or 

 copper. 



The different varieties of garnet differ very considerably in value. The worth of a 

 stone depends for the most part on the beauty of its colour and the rarity of its occur- 

 rence. Particulars as to prices will be given later on under the description of different 

 varieties. 



The commonest fault in garnet is the presence of fissures along which the stone is apt 

 to fracture. Garnets are often, however, almost ideally pure ; they are transparent and 

 faultless much more frequently than are many other precious stones. 



Garnet is one of the most important of minerals, the common, imperfectly transparent 

 varieties being widely distributed throughout the earth's crust. Transparent precious 

 garnet is less abundant, but occurs under exactly the same conditions. Garnet is for the 

 most part a mineral characteristic of the ancient crystalline-silicate rocks, especially 



