ADDENDA.
511
the fix facets, three are heptagons, and threerhombs.
4. A nine-fided prifm, terminated as above.Of the fix facets, the three larger are hexagons,and the three fmaller irregular heptagons.
5. A nine-fided prifm, terminated at oneextremity by feven, and at the other by threefacets. Of the feven, fix are alternately rhombsand parallelograms furrounding an equilateraltriangle.
6. A nine-fided prifm, terminated as thepreceding. Of the feven faces, fix are alter-nately triangles and pentagons furrounding atriangle.
7. A twelve-fided prifm, with nine faces oneach fummit.
8. A nine-fided prifm, with nine faces onone fummit, and three on the other. Of thenine faces, three are rhomboidal, and form theterminating pyramid, the other fix are formedby tru'ncatures of the common bafe of the pyra-mid and prifm.
9. A nine-fided prifm, one of the fummits ofwhich is unknown, the other is a pyramid com-pofed of three lengthened hexagons with twotrapeziums intervening between each.
10. A nine-fided prifm, one of the fummits
of which is unknown; the other is compofedof 15 faces, viz. three pentagons, three triangles,three rhombs, and fix parallelograms.
11. A twelve-fided prifm, one of the fum-mits of which is unknown, the other is com-pofed of 19 facets.
12. A twenty-four tided prifm, one of thefummits of which is unknown, the other iscompofed of fix facets, alternately large andfmall.
The prifms are generally long in proportionto their thicknefs, and longitudinally ftriated.The internal luftre is more or lefs fhining,between vitreous and refinous. The longitudi-nal fracture is conchoidal, palling in the blackvarieties to coarfe-grained uneven; the crofsfradture has a tendency to foliated. It variesfrom tranllucent to opake. Its hardnefs isabout equal to that of quartz. It is eafilyfrangible. Sp. gr = 3.09—3.15.
Before the blow-pipe it is fufible by itfelf,without much difficulty. By friction it exhi-bits the vitreous electricity at each extremity;by heating, one end exhibits the vitreous, andthe other the refinous electricity. The follow-ing are- the principal analyfes that have beenmade of it.
Black S.in mafs.
D° Cryltal-lized.
D° fromCeylon.
D° from
Brafil.
... n
V
—-y-
Gerhard
Bergman
Vauquelin
40.
38. Silex
40.
37-
34. Silex
40. Silex
25. 1
20. Alumine
42.
39-
50. Alumine
39. Aiumine
15-
2o. Lime
12.
15
11. Carb. Lime
3.84 Lime
18.
19- Iron and
6.
9-
5. Ox. Iron
12.5 Ox. Iron
Manganefe
2. Ox. Man
—
—
100.
100.
100.
--
98.
97-
■■
•
97-34
Schorl occurs in primitive rocks, efpecially ingneifs and granite, in micaceous and argillaceous, ichiftus. It often is imbedded in quartz, butnever, we believe in felfpar. The opake blackvarieties with a granular fradture are calledfchorl, the others are called tourmaline.