412 
DESCRIPTIVE MINERALOGY. 
Oxide of zinc, 
Oxide of iron, 
Carbon,. 
I. II. 
96.10 95.00 
2.90 4.50 
1.00 0.50 
It is, therefore, a nearly pure oxide of zinc. The above results agree very well with those 
obtained from an examination of similar products in France. 
ORDER IV. LEAD. 
Galena. 
4. Yellow Lead Ore. 
White Lead Ore. 
5. Pyromorphite. 
Anglesite. 
6. Vauquclinite. 
GALENA. 
[From the Latin galena , an ore of silver and lead.] 
Plomb Sulfure. Tlainj. — Sulphuret of Lead, or Galena. Cleaveland. — Sulphuret of Lead. Phillips and Thomson. 
— Hexahedral Galena, or Lead Glance. Jameson. — Hexaedrischer Blei-Glanz. Mohs. — Galene. Beudant. 
Description. Colour bluish grey, usually called lead-grey. Streak unaltered. It occurs 
regularly crystallized ; also granular and massive, sometimes having a lamellar structure, and 
at others almost compact. The primary form is a cube, Fig. 488. 
Cleavage parallel with the primary planes, highly perfect, and easily 
obtained. Fracture even, or flat conchoidal. Very frangible and sectile. 
Lustre brilliant metallic. Opaque. Hardness from 2.5 to 3.0. Spe¬ 
cific gravity from 7.40 to 7.65. Fusible before the blowpipe, with 
the disengagement of fumes of sulphur. When heated on charcoal, 
the metallic lead is obtained. Soluble in nitric acid, forming a white 
precipitate of sulphate of lead. When dissolved in dilute nitric acid 
with only a slight elevation of temperature, the solution produces a 
precipitate of brilliant blades of lead upon a clean plate of zinc, but not upon a plate of cop¬ 
per, unless it contains sulphuret of silver. 
Composition. Lead 85.13, sulphur 13.02 (Thomson). This is nearly in the ratio of 
one atom of each of the constituents ; but it often contains small quantities of sulphuret of 
silver. Formula PbS. 
