QUARTZ WITH ENCLOSURES 489 



QUARTZ WITH ENCLOSURES. 



We have already seen that quartz frequently encloses other minerals and foreign 

 substances of various kinds. These enclosures may be present singly in comparatively small 

 numbers or in such multitudes as to impart an apparently uniform colour to the quartz 

 substance, as is the case \\'ith prase and with sapphire-quartz just described. It is proposed 

 to consider here those cases in which there are present single enclosm-es of a nature to 

 contrast very markedly with the quartz in which they are embedded. It is obvious that 

 enclosures in translucent or opaque quartz will be seen very indistinctly or not at all, so that 

 it is only the enclosures in very transparent quartz which ^\ill engage our attention. On 

 the other hand, the clearness with ^\hich enclosures in quai'tz are seen is not at all affected 

 by the colour of the mineral, objects embedded in amethyst being quite as distinctly seen as 

 those in rock-crystal. These two varieties of quartz are those which most commonly 

 contain enclosures, the different kinds of which will be described below in some detail. 



Hair-stoue and Needle-stone. — These names are given to quartz with enclosures 

 of isolated, needle-like or hair-like crystals of various substances, like that represented in 

 Plate XVIII., Fig. 2, which encloses green needles of actinolite. In other cases the 

 enclosures may be white fibres of asbestos, long, thin crystals of rutile ranging in colour 

 from yellow to red and somewhat resembling straw in appearance, and so on. Quartz 

 containing enclosures of this description is distinguished as needle-stone or as hair-stone 

 according as the enclosed crystals approach more to the thickness and straightness of a 

 needle, or to the fineness and sinuosity of a hair. Enclosures of rutile of a reddish-brown to 

 yellow colour, are referred to as " Venus's hair," and the stone as a whole as " Venus's 

 hair-stone." Enclosures of green hornblende, actinolite, or asbestos are often called 

 "Thetis's hair." The fibres may be straight, bent, crumpled, or wound into a ball. The 

 appearance of green fibres, probably of asbestos, embedded in quartz often resembles that 

 of a piece of moss, and the quartz containing such an enclosure is known as moss-stone ; 

 such moss-like enclosures are also frequent in agate (moss-agate), to be considered 

 further on. 



Enclosures of various kinds are not at all uncommon in the rock-crystal from the Alps 

 and other localities. Some specimens of rock-crystal from Madagascar enclose long grey 

 crystals of inanganite with a bright metallic lustre. From the Calumet 

 Hill quarry, near Cumberland, in Rhode Island, U.S.A., is obtained a 

 translucent, milk-white quartz containing numerous needles of black 

 hornblende ; a large amount of this material was formerly exported 

 for cutting to Idar and Oberstein on the Nahe, but since 1883 the 

 supplies have ceased. Similar material is obtained in Japan and 

 Madagascar. 



In the pale amethyst found in the amygdaloidal cavities of rocks 

 or loose in the soil of Wolfs Island, in Lake Onega, north-east of fig. ss. Fl&ches 

 St. Petersburg, there are long brown crystals of the mineral gothite d'amour from Wolf s 

 (" needle-iron-ore ") (Fig. 88) ; and there are many other similar occur- p ' ' . ' ' '^ "®^"' 

 rences. These stones are cut in St. Petersburg and Moscow under the name 

 of " Cupid's darts " {Jteches (Tamour). The same name is used for other stones of similar 

 appearance, such, for example, as the beautiful specimens which occur in North Carolina, 

 U.S.A. Like all mineral objects of the kind they are provided with a slightly convex 

 polished surface, and often cut with a heart-shaped outline. Whether such objects are cut 



