1 R O

JRO (' 581 )

B.

S.

96.5 —

98.5 Iron

3-5 —

1.5 Nickel

IOO —

IOO

The proper native iron of Kamfdorf in Sax-ony , according to the fame authority, is com-pofed of 9 2 *5 Iron

6.0 Lead1.5 Copper

100.0

Sp. 2. Unmagnetical Iron Pyrites.

Of this there are the five following fub-fpecies.

i.&ubfp. Common Pyrites. Gemeiner Sehivef-elkies. Wern. Pyrite martiale commune. Broch.

Its colour is perfect brafs-yellow, fometimesby tarnifhing it is fuperficially reddifh or brown-ipi.

It occurs maffive, diffeminated, inverting, andcryftallized. Its primitive cryftalline form is thecube, which pafles into the following varieties :

1. The cube, with convex faces.

2. The cube with folid angles replaced bytriangular facets, fo as to be intermediate be-tween the cube and octohedron.

3. The cube with its edges replaced by nar-row planes inclined more towards one than theother of the adjacent faces.

4. The cube with the three plane angles thatform each of the folid angles, replaced by fe-condary angles of more than 90°.

5. The octohedron either perfect or with allits folid angles replaced by planes.

6. The dodecahedron with pentagonal faces.

7. The fame, with fix oppofite and paralleledges replaced by narrow planes.

8. The dodecahedron with eight of its anglesreplaced by planes, forming the paffage into theicofahedron.

9. The perfect icofahedron. This variety isextremely rare.

10. The fame, with four edges replaced bynarrow planes.

11. The triacontahedron, formed of thirtyrhombic faces.

The cryftals are moftly fmall, but the cubesare often middle-fized; they are fometimesfingle, but oftener varioufly aggregated. Thefurface of the cryftals is generally fmooth, butthe cubes fometimes occur ftriated in threedirections; their luftre varies from fpecular to

gliftening. Internally it is feebly-fliinirig, witha metallic luftre. Its fracture is coarfe or fine-grained uneven. Its fragments are indetermi-nately angular. It does not yield to the knife;and gives red fparks with fteel: it is opake,brittle, not very frangible, and by percuflionaffords a fulphureous odour. Sp. gr. of thecryftallized, 4.78 : 4.83.

When expofed to the blowpipe on charcoal,it emits a ftrong fulphureous odour, and burnswith a bluifh flame. It then becomes a brownifhglobule, attractable by the magnet, and by afurther continuance of the heat paffes into ablackifh flag.

According to the experiments of Mr. Hatch-ett, h the pyrites with fmooth cubes confifts ofSulphur 52.70Iron - 47.30

100.0

Pyrites with ftriated cubes containsSulphur 52.5Iron - 47.5

100.0

and dodecahedral pyrites contains'Sulphur 52.15Iron - 47.85

100.00

The ftriated cubes and dodecahedrons fome-times contain gold, and hence are named auri-ferous pyrites.

Common pyrites occurs in almoft every mine-ral formation, and almoft every fpecies of rock.It abounds in granite, and particularly in primi-tive and tranfition argillaceous fchiftus.

It is never wrought as an ore of iron, but islargely employed in the manufacture of greenvitriol, and fulphur is often procured from itby fublimation, while the refidual red oxyd isvaluable as a coarfe kind of paint.

2. Subfp. Radiated Pyrites. Strahliies. Germ.Pyrite rayon nee. Broch.

Ifs colour is brafs-yellow, but paler than com-mon pyrites; its furface is generally tarnifhed.It occurs in mafs, but molt ufually in particularforms, fuch as kidney-fliaped, tuberous, globular,botryoidal, fcaly, ftalaCtitic, &c. Alfo in mi-nute cryftals between the cube and oCtohedron.When the cryftals are very much flattened andunited in diverging groups, they form the cock’s-comb pyrites. The furface ot the cryftals is

1 Phil. Tranf; xciv. p, 3J5.

4 C 2