a en et se. 
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| QUARTER. 
made to communicate with the train, and this must 
be so arranged as to give the person firing it time to 
retreat before the powder explodes, as fragments of 
the stone are frequently dispersed with such violence 
as to be very dangerous. ‘Che most hazardous thing 
in shooting a hole, as miners call this operation, is 
when, by improper fixing of the match, the whole 
charge explodes the instant the fire touches it, or 
where it hangs fire, or is so long before it explodes 
|| that the workman imagines the match has been ex- 
tinguished; and, perhaps, goes to inspect it at the 
very time when it expledes. From both these 
causes very serious accidents have occurred, and no 
/| one owght to approach a hole after the match has 
been lighted, until such a period has transpired as 
must render an explosion impossible. 
As marble and granite have always to be 
transported, unless used upon the spot where 
they are produced, it may be useful to remark, 
that fourteen cubic feet are considered as equal 
to a ton weight, on which account a considerable 
loss frequently accrues to the purchaser; for the 
cubic quantities are taken by weight, to deter- 
mine the freight, instead of by measurement ; 
the cubic fect rarely measure to what is marked 
ticularly when it is hard, good, and compact. 
But lighter and more porous stone will, on the 
ton.: 
QUARTER. The fourth part of any thing ; 
er a division of a carcase comprising one of the 
limbs; or twenty-eight pounds weight; or a 
measure of grain equal to eight bushels. 
QUARTER-ILL. See Inrnammatory Fryer. 
QUARTZ. <A well known mineral species, 
which surpasses all others in the extent of its 
distribution. It is also one of the mest compre- 
hensive in the varieties it embraces, which are 
especially numerous as respects colour, lustre, 
and fracture. Its contents have very improperly 
been swollen, however, by the introduction of 
many substances which consist of mixtures of 
quartz with other species; and the difficulty of 
forming a correct idea of this group of minerals 
has been enhanced by their being separated into 
several species and sub-species, as has been done 
in certain treatises on mineralogy. 
endeavour, in the first place, to take a scientific 
view of quartz; after which we shall point out 
|| those varieties which have, from various causes, 
obtained distinct appellations, together with the 
mixtures of quartz with other minerals, usually 
'| considered as varieties of the species; and, 
|| finally, the varieties which are employed in the 
arts. 
The crystals of quartz are; for the most part, regular 
_| six-sided prisms, terminated at one or both of their 
extremities by six-sided pyramids, the faces of which 
correspond to the sides of the prism, and meet under 
an angle of 141° 40’. It sometimes happens that the 
prism intervening between the two pyramids is very 
short, or even extinet; in which case the form be- 
comes the dodecahedron, with isosceles triangular 
faces. In the six-sided prism with pyramidal terimi- 
nations, we often observe the solid angles, situated 
and as the above proportion is not a true one, 
upon the stone, or what they are sold for, par-_ 
contrary, yield more than fourteen feet to the. 
We shall | 
— QUARTZ. 3 
between the prism and the pyramid, replaced by 
rhomboidal planes. ‘The alternate faces of the prism 
are striated horizontally. The primary form is a 
rhomboid of 94° 15’ and 85° 43’, parallel to whose 
planes cleavages may be obtained, as also to the planes 
of the dodecahedron, with isosceles triangular faces, 
which might also be regarded as the primary form of 
the species; but the former figure is preferred on ac- 
count of its simplicity. Lustre vitreous, inclining, 
in some varieties, to resinous; coleur white preva- 
lent; among the brightest colours are violet-blue, 
rose-red, clove-brown and apple-green. Dark brown 
and green colours are generally owing to foreign ad- 
mixtures Streak white; transparent, translucent, 
frequently opaque, but never, perhaps, unless occa- 
sioned by other minerals; hardness between felspar 
and spinelle; specific gravity 2-69. The crystals 
often present macles, and sometimes we observe 
larger crystals, apparently made up of innumerable 
smaller ones, all of which are so aggregated that their 
similar faces coincide as respects direction. Implanted 
globules, reniferm and stalactitic shapes, are other 
modes of occurrence with compound varieties ef this 
species. These have smooth, granulated and drusy 
surfaces ; composition (mechanical) columnar, often 
impalpable, and frequently a secend time composed 
into granular or curved lamellar masses. The mas- 
sive varieties present a granular or columnar, and 
often an impalpable composition, in which case the 
fracture becomes concheidal and splintery. Some- 
times a second composition produces indistinct granu- 
lar or thick lamellar masses. Certain very thin co- 
lumnar compositions, if cut en cabuchon, parallel to 
the fibres, show an opalescent light. We have pseu- 
domorphous crystals, also, ef this species, in the 
shape of cubes, octahedrons, and various other forms, 
derived from fiuor, calcareous spar, gypsum, &c. be- 
sides which, quartz occurs in globular and tuberose 
masses, formed in vesicular cavities, and also in plates 
and pebbles. The principal varieties of quartz, which 
are known by distinct names, are the following: 1. 
rock crystal; 2. smoky quartz; 3. yellow quartz; 4 
amethyst ; 5. siderite, or blue quartz; 6. rose quartz ; 
7. miiky quartz ; 8. irised quartz ; 9. common quartz; |. 
10. fat (greasy) quartz; ll. flint; 12. hornstone ;— 
13. Lydian stone; 14. floatstone (swimming stone) ; 
15. fibrous quartz ; 16. radiating quartz; 17. chalce- 
dony; 18. carnelian; 19. chrysoprase; 20. agate. 
Rock crystal is applied to the transparent and colour- 
less crystals, and more particularly to those of a large 
size. Smoky quartz consists of those crystals and 
crystalline masses which are translucent and of a 
brown colour. Yellow quartz, sometimes called, also, 
Bohemian or Scottish topaz, is transparent, and of 
various shades of yellow. Amethyst, also in crystals, 
and for the most part nearly transparent, is of every 
shade of violet. Siderite, or blue quartz, is never in 
regular crystals, but usually compact, and of an azure- 
blue colour. Rose quartz is confined to translucent 
massive varieties, of a delicate rose-red colour. Milky 
quartz is also massive, having an uneven fracture, is 
translucent, and of a milk-white colour. -Irised 
quartz embraces such crystallized varieties as exhibit 
in patches, at or beneath the surface, the colours of 
the rainbow. Common quartz differs from milky 
quartz simply in being destitute of the milky white- 
ness of that variety, or in having an inferior degree of 
whiteness, and more of a vitreous lustre. Fat or 
greasy quartz differs from common quartz merely in 
lustre, which, instead of being vitreous, has the ap- 
pearance of having been immersed in oil. Flint has 
a more compact texture than common quartz, is dull, 
only translucent on the edges, of a brownish colour, 
and breaks with a conchoidal fracture. Hornstone 
closely resembles flint, from which it can scarcely be 
distinguished, except in its conchoidal fracture, which 
is much less distinct. When replacing the fibres of 
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