THE GARNET GROUP (HESSONITE) 351 



of hcssonite for hyacinth is not clone with the object of deception, but arises solely from 

 confusion of names : although the lustre of hyacinth is far superior to that of hessonite, yet 

 the colour of the latter is quite equal to that of hyacinth. A perfectly transparent, finely 

 ■coloured, and faultless cinnamon-stone cannot, therefore, be any more inferior to hyacinth in 

 value than it is in beauty of appearance. 



Although hyacinth and hessonite are frequently mistaken the one for the other in the 

 trade, yet their discrimination is really a simple matter. Hyacinth is much heavier than 

 hessonite, for while the specific gravity of the latter lies between 36 and 3-7, that of 

 hyacinth ranges from 4'6 to 4-'7. Hessonite again is singly refracting, while hyacinth has 

 strong double refraction. The lustre of the two stones differs also, that of hyacinth being 

 stronger and more adamantine in character, while that of hessonite is strongly vitreous 

 inclining to resinous, grains of hessonite being particularly resinous in appearance. 

 Moreover, hyacinth is somewhat harder than hessonite ; for the former H = 7^, while foi- 

 the latter H = 7 J, so that hessonite is only slightly harder than quartz. To distinguish 

 between hessonite and yellowish-red spinel (rubicelle), on the other hand, is less easy, for 

 the colour of the latter often closely resembles that of hessonite ; moreover, the two stones 

 both crystallise in the cubic system and are therefore singly refracting ; they are of about 

 equal hardness and very nearly the same density, the specific gravity of spinel being slightly 

 less, namely, 3'60 to 3"63, and its hardness rather greater, namely, H = 8. Under these 

 circumstances it is sometimes impossible to say whether a faceted stone or an irregular- 

 fragment is hessonite or spinel. When the crystalline form is observable it is easy, however, 

 for spinel always crystallises in octahedra, while hessonite rarely takes this form, but more 

 often that of Fig. 69d. The refractive indices of the two stones are also almost the same. 

 The only certain means of distinguishing between stones similar or identical in so many 

 respects is to make a chemical analysis, and this in the case of faceted stones is not always 

 feasible. A glass imitation can, of course, be easily distinguished by its hardness and specific 

 gravity. 



A few other characters of cinnamon-stone remain to be mentioned. The index of 

 refraction is slightly less than that of other garnets ; for red light n — 1'74 ; anomalous 

 double refraction is sometimes to be observed. Hessonite fuses to a greenish glass somewhat 

 readily when heated before the blowpipe. Although it contains only a small amount of 

 iron, the mineral has a slight action on the magnetic needle. 



It has been mentioned already that hessonite occurs in Ceylon ; this island (Fig. 59) 

 is almost the only locality for hessonite of gem-quality, and it is probable that all the stones 

 on the market come from thence. It is found in smaller or larger fragments, some lying- 

 loose, some still in the solid rock, which is gneiss containing actinolite, magnetite, and other 

 minerals. Blocks of considerable size containing portions of gem-quality are found, 

 amongst other localities, at Belligam, a few miles from the Point de Galle. It is the 

 rounded pebbles found in the gem-gravels, especially in the district of Matura, which are 

 most used for cutting as gems. These pebbles, the largest of which are several pounds in 

 weight, are finer and purer and less fissured than are the angular fragments which have not 

 been water-worn. These also, however, are traversed by cracks and fissures, the presence of 

 which is the commonest, and almost the only fault usually present in cinnamon-stone. 



The hessonite which occurs at other localities is less suitable for cutting, the specimens 

 being small or imperfectly transparent. Still, there are a few localities in Europe, 

 especially in the Alps, which yield, or have yielded, a small amount of hessonite of gem- 

 quality. In early times fine " hyacinth-garnets from Dissentis " or " from St. Gotthard " 

 were sometimes cut as gems. They occur with epidote in quartz in a small crevice in mica- 



