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POPULAR SCIENCE REVIEW. 
shows crystals of the variety called smoky quartz, which varies in 
colour from a very dark, almost opaque, to a light brown smoky 
tint. The colours of the varieties of smoky quartz and cairn- 
gorm are materially increased by exposure to heat, as in the 
example (fig. 12), a property frequently taken advantage of by 
jewellers when mounting such stones. 
The cairngorm was invariably used as a decoration of the 
Highland dress. The breast-buckle, or brooch, from the earliest 
times has always been a favourite personal ornament in Scot- 
land. Martin, in his work on the Western Isles, published in 
1703, says: ‘‘I have seen some of the former of an hundred 
marks’ value. It was broad as any ordinary pewter plate, the 
whole curiousl}^ engraven with various animals, &c. There was 
a lesser buckle, which was worn in the middle of the larger, and 
about two ounces in weight. It had in the centre a large piece 
of crystal or some finer stone, and this was set all round with 
several stones of a lesser size.’ 
Among remarkable relics of this kind is the Grlenlyon brooch, 
which is circular, and of silver, richly jewelled ; and the still 
more celebrated brooch of Lorn, dropped by Eobert the Bruce 
after the defeat of his followers at Methven,* and alluded to by 
Sir Walter Scott in the ‘‘ Lord of the Isles” : — 
Whence the hrooch of burning gold, 
That clasps the chieftain’s mantle-fold, 
Wrought and chased with rare device, 
Studded fair with gems of price.” 
Various other varieties of quartz, such as rose, blue, leek- 
green (prase), and aventurine quartz, are also met with in Great 
Britain, and might be employed in jewellery, although seldom 
found of much beauty. 
The term Cat’s-eye has been applied to a variety of quartz 
which possesses a peculiar opalescent structure, due to the 
presence of minute parallel fibres of amianthus imbedded in its 
substance. This variety, which in jewellery is always cut en 
cahochon, has been found in the Vale of Llanberis in Wales, 
and also in Scotland. ^ ^ 
The varieties of silica in which crystallisation is not dis- 
tinctly visible, form a large class of stones employed in the 
manufacture of the chief articles of personal decoration, and 
many of which are extremely pretty. These are generally 
classed under the term calcedony, which is translucent, and 
frequently found associated with more or less admixture 
of crystalline quartz. The reddish-yellow, brown, milky, and 
mottled varieties of calcedony are usually known as cornelian, 
* Figures of these beautiful examples of the favourite Celtic ornament 
are given in D. Wilson’s “ Prehistoric Annals of Scotland,” plates 2 and 3. 
