QUARTZ (AMETHYST) 481 



England as cairngorm. The search for crystals of smoky-quartz was formerly a very 

 profitable industry in the districts contiguous to the great granite masses in this part of 

 Scotland, but it has now been practically abandoned. The cairngorms were obtained by 

 digging shallow pits and trenches in the decomposed granite and debris which covers most 

 of the flat hill-tops, and also appears in many of the corries. The mineral occurs, together 

 with large crystals of orthoclase and plates of muscovite-mica and sometimes beryl, lining 

 cavities in veins of fine-grained granite which penetrate the coarse gi"anite. 



Material suitable for cutting is met with at several localities in the United States. 

 Large quantities, associated with amazon-stone, are found in the coarse-grained granite 

 of Pike's Peak, in Colorado, where several thousand dollars' worth of stones are collected 

 and cut every year. The largest crystal found at this locality is over 4 feet long. At 

 Mount Antero, in Colorado, at Magnet Cove, in Arkansas, and in Burke and Alexander 

 Counties, North Cai'olina, smoky-quartz is obtained in not inconsiderable amount. Pebbles 

 of smoky-quartz, and also of I'ock -crystal, are not uncommon on the coast at Long 

 Branch, near Cape May, New Jersey, and are cut and bought by visitors as souvenirs. 

 It would be superfluous, even if it were possible, to enumerate all the many localities 

 for smoky-quartz in the United States. It may be mentioned, however, that here 

 also occur crystals of very large size, weighing upwards of a hundredweight, of the 

 most perfect transparency, and constituting some of the finest of gems. 



Smoky-quartz is usually cut as a brilliant or table-stone, sometimes also in the step- 

 cut, the form with elongated brilliant facets, or the Maltese cross (Plate XVIII., Figs. 36, c). 

 Under the name of cairngorm it is specially admired as a gem in Scotland. Besides being 

 cut as a gem, smoky-quartz, like rock-crystal, is fashioned into a variety of semi-ornamental 

 objects, its strong lustre and rich colour being displayed by such articles with good effect. 



There are but few precious stones of a brown coloui', and of these smoky-quartz is the 

 most transparent, and also the most abundant. The brown precious stones for which it 

 might conceivably be mistaken are axinite, idocrase, and brown tourmaline ; others are of a 

 more yellowish-brown colour, and therefore distinguishable at a glance from smoky-quartz. 

 Each of the three minerals mentioned above is heavier than sinoky-quartz, and the specific 

 gravity of each being greater than S'O they all sink in liquid No. 3, in which smoky-quartz 

 floats. Moreover, smoky-quartz is only feebly dichroic, while the other three are strongly 

 so. Brown diamond, which may resemble smoky-quartz in colour, is readily distinguished 

 by its strong and characteristic lustre, its single refraction, complete absence of dichroism 

 and high specific gravity, the last named character causing it to sink heavily even in pure 

 methylene iodide. 



AMETHYST. 



Amethyst, or occidental amethyst as it is called in order to distinguish it from 

 " oriental amethyst," is quartz of a violet colour. The range of colour includes reddish- 

 violet tints of pale or almost colourless shades, and deep, rich tones of pure violet. It is 

 not uncommon for this stone to show patches of different shades of colour or colourless 

 portions side by side with those of a violet colour, these differently coloured portions being 

 sometimes arranged in regularly alternating bands or sectors. In a few rare cases crystals 

 showing a second colour — yellow or green — have been met with. 



Generally speaking, amethyst is cloudy: perfectly clear and transparent material is 

 distinguished as precious amethyst ; the latter alone is cut as gems, which are estimated 

 according to their transparency and their depth and uniformity of colouring. Pale-coloured 



2h 



