456 SYSTEMATIC DESCRIPTION OF PRECIOUS STOxNES 



with true chrysobei-yl and was formerly mistaken for this stone, and it is probable that 

 many supposed chrysoberyls from Brazil would turn out on closer examination to be 

 spodumene. A few transparent pebbles of a beautiful blue colour were found formerly in 

 the Rio de S. Francisco in the neighbourhood of Diamantina in Minas Geraes, and these 

 for a long time were mistaken for blue lazulite. 



Hiddenite can be distinguished from other green precious stones without much 

 difficulty. The differences between this stone and emerald have been ali-eady pointed out. 

 It is distinguished from chrysoberyl by the fact that it is much softer and much lighter, 

 hiddenite floating in methylene iodide and chrysoberyl sinking heavily. Diopside differs 

 from hiddenite in its specific gravity, which is higher, and its feeble dichroism ; and the 

 same is true also of chrysolite. Demantoid, the green variety of garnet, is often very 

 similar in colour, but it is singly refracting, and therefore cannot be mistaken for the 

 doubly refracting and dichroic hiddenite. 



RHODONITE. 



Rhodonite is a member of the pyroxene group, remarkable for its rose- or raspberry-red 

 colour, which, however, in some cases may incline to a light chestnut-brown. The mineral 

 is used as a gem and also is fashioned into all kinds of ornamcnlal objects ; the sarcophagus 

 of Czar Alexander II., for example, is constructed entirely of rhodonite. The material used 

 for such purposes is found at Ssedelnikova, in the neighbourhood of Ekaterinburg, in the 

 Urals ; it is finely granular to compact, and has a somewhat splintery fracture. It is 

 worked for the most part at Ekaterinburg. The locality is situated on the eastern side of 

 the Urals, south-west of Ekaterinburg and on the right bank of the Amarilka, a tributary 

 on the right of the Isset ; it is distant only a few versts from the gold-washings of 

 Shabrovskoi. The rhodonite is here obtained from the (juarries, which lie close together, 

 in what appears to be a black clay-slate. The upper portion of the deposit contains a large 

 admixture of quartz, and is therefore unfit for use. The rhodonite in places is very coarse- 

 grained ; such material, though unsuitable for cutting, is of interest mineralogically, since 

 its nature can be easily made out. The whole deposit is penetrated by numerous cracks 

 and fissures, the course of which is indicated by a black discolouration, due to weathering 

 of the material along these cracks. 



Rhodonite of the same description is also found, though less abundantly, in the 

 manganese deposits of Wermland, Sweden ; the material from this locality is not used for 

 cutting. The American occurrence at Cummington, in Massachusetts, is more important. 

 Here are found blocks of rhodonite, of a fine, rose-red colour and several hundred pounds in 

 weight. The material is equal in quality to that from Russia, and is used for similar 

 purposes. 



Chemically, rhodonite is a silicate of manganese, which, when pure, has the formula 

 MnO.SiOj. Usually other constituents are present, especially calcium and iron, in greater 

 or less amount. Crystals belonging to the trichnic system are met with not infrequently, 

 but at localities other than the Urals. Very good ones are found, for example, in the 

 manganese mines in Wermland. These are transparent and of a beautiful colour, but on 

 account of their small size ai-e scarcely ever cut as gems, the massive material already 

 mentioned being the variety worked almost exclusively for decorative purposes. Massive 

 rhodonite has a hardness which lies between 5 and 6, and a specific gravity which varies 



