THE GARNET GROUP (ALMANDINE) 353 



A remarkable phenomenon connected with ahnandine and with only one other 

 precious stone, namely zircon, is the presence of dark absorption bands in the spectrum of 

 light which has passed through the stone. In the case of almandine the characteristic black 

 bands occur in the green part of the spectrum, and can be seen with the aid of an ordinary 

 pocket spectroscope. These absorption bands are perfectly characteristic of almandine and 

 distinguish it from all other precious stones. The phenomenon affords an easy means of 

 discriminating between almandine and red spinel, both of which are singly refracting and 

 therefore devoid of dichroism. 



Almandine in colour often approaches very closely to ruby, but may be readily 

 distinguished from the latter by its single refraction and absence of dichroism. The two 

 minerals differ also in specific gravity, that of ruby scarcely exceeding 4"0 while that of 

 almandine varies between 4'1 and 4'3, a value which is higher than for any other garnet. 

 Again, almandine is only slightly harder than quartz, its hardness being 1^, so that it is 

 scratched by topaz and still more easily by corundum or ruby. 



Not only is almandine heavier than hessonite, but its optical refraction is greater also, 

 the refractive index of the former for red light being n = 1*77. Before the blowpipe 

 almandine fuses to a magnetic mass with moderate ease. Even before fusion almandine has 

 a slight action on the magnetic needle like hessonite, the action of which is feebler, howevei", 

 since it contains less iron. 



Though not as brilliant as ruby, almandine, when cut and polished, has a fine lustre. 

 It is cut usually in the forms adopted for other garnets. Fig. 4 of Plate XIV. represents a 

 rosette of almandine. This stone is frequently also cut en cabochon (Plate XVIII., Fig. 7), 

 more often than is hessonite, for example. Stones treated in this way are usually hollowed 

 out, and are then known as garnet-shells ; their colour is then not too deep and the lustre is 

 advantageously displayed by the curved surface. Foils of burnished metal placed beneath 

 the stone produce a fine effect. 



The value of a stone depends on its size and purity, on the absence of faults, especially 

 fissures, and in particular on its colour, which must show up brightly even if the stone be 

 of considerable thickness. The nearer it approaches the fine, lustrous, velvety-purple 

 of the ruby the gi'eater will be the value, and the price of such stones may reach that of 

 sapphires of medium quality. Stones of a brownish tinge, like the vermeille garnets, are 

 little prized and are very cheap, as are also those of small size, impure colour, or with 

 fissures or other faults. 



Cloudy and opaque almandine of a quality not suitable for gems is the most widely 

 distributed of all garnets. It is the common garnet of mineralogists, and is found in very 

 well-developed crystals, sometimes many pounds in weight, in gneiss and mica-schist, 

 sometimes also in granite and other rocks. This mode of occurrence is illustrated in 

 Plate XIV., Fig. 3. Transparent precious garnet, such as is used for cutting as gems, 

 occurs together with, and in the same manner as, the cloudy and opaque garnet, though 

 the former is of more sparing occurrence than the latter. As is the case with so many 

 other precious stones, almandine does not always remain in its original mother-rock, but is 

 often set free by the weathering of the rock, and ultimately becomes a constituent of the 

 sands and gravels of running streams, from which it is obtained in the form of rounded 

 pebbles. Almandine of gem-quality is not only more abundant than hessonite, but is also 

 more widely distributed. The more important localities are detailed below. 



The locality standing first in importance, at which both hessonite and almandine occur, 

 is Ceylon. Pebbles of almandine suitable for cutting are here, however, smaller and far 

 less abundant than are those of hessonite. Near Trincomalee, on the eastern side of the 



