488 SYSTEMATIC DESCRIPTION OF PRECIOUS STONES 



ROSE-QUAETZ. 



Rose-quartz (" Bohemian ruby ■") is a translucent or semi-transparent, massive quartz 

 with a somewhat greasy lustre and a fine rose-red colour. This colour is not permanent, but 

 quickly disappears on exposure to light or a high temperature. It is probably due to the 

 presence of some organic matter, but has also been ascribed to titanium dioxide, small 

 amounts of which have been found in rose-quartz. Specimens showing paler shades of the 

 same colour merging imperceptibly into milk-white are not uncommon, and contrast well 

 with those of the typical rose-red colour. Stones of a deep shade of this colour are cut with 

 a rounded surface, but are not in much favour and are very low in price. In spite of this, 

 rose-quartz is imitated in glass, so cleverly indeed that it is sometimes only possible to 

 distinguish between the two by the lower specific gravity, greater hardness, and double 

 refraction of the quartz. The mineral is found in large irregular masses in granite in the 

 neighbourhood of Bodenmais in Bavaria, and of Ekaterinburg in the Urals, and in Ceylon, 

 India, Brazil, &c., but must always be classed with the less widely distributed varieties 

 of quartz. 



PRASE. 



Prase is sometimes referred to by jewellers as " mother-of-emerald " in reference to the 

 fact that it was formerly supposed to be the mother-rock of the emei'ald. It is a translucent 

 variety of quartz with a somewhat greasy lustre and a leek-green colour. This last named 

 character is due to the presence of innumerable minute fibres and needles of actinolite 

 enclosed in the otherwise colourless and pure mass of quartz. Prase was known to the 

 ancients, and was used in the fashioning of ornamental stones and to represent foliage in 

 mosaics, while as a gem it was frequently engraved. In the latter form it is not uncommon 

 among Roman remains, but the source from whence the Romans obtained their rough 

 material is not now known. There are many more recently discovered localities however ; 

 thus crystals and crystalline masses, of the same quality as the material used by the ancients, 

 occur in metalliferous veins with iron-pyrites and zinc- blende at Breitenbrunn between 

 Schwarzenberg and Johanngeorgenstadt in the Saxon Erzgebirge. Also in the Habachthal, 

 in the Salzburg Alps, and at several places in Scotland, Finland, &c. Prase is applied now 

 to the same purposes as in ancient times, but to a very limited extent, and this, combined 

 with its abundance in nature, makes it one of the lowest pi'iced of ornamental stones. 



SAPPHIRE - QUARTZ . 



Sapphire-quartz (azure-quartz or siderite) is a blue, crystalline quartz, the colour of 

 which is due to the enclosure of a large amount of a blue, fibrous to earthy substance 

 belonging probably to the mineral species crocidolite. It is only faintly translucent, has a 

 slightly greasy lustre, and is not very suitable for cutting, hence it is used to a very small 

 extent and is con-espondingly low in price. It occurs in moderately large amount in veins 

 penetrating the gypsum of the Gypsberg at Mooseck, near Golling, in Salzburg. 



