difficult of access, nor at an inconvenient distance from the town, most of them being contained in a circle of two English miles.
The metalliferous veins of this district are found principally in the Phyllade, (Thonschiefer, or Clay Slate,) which contains in subordinate strata, 1. Le traumate, (Grauwacke;) 2. Le traumate schisteux, (Schieffrige Grauwacke, or Greywacke Slate;) 3. Le Calcaire, (Transition Limestone;) 4. Le Talcschisteux, (Talkschiefer;) 5. Le Feldspath Compacte, (Prismatic Feldspar of Jameson;) 6. Le Diabase, (principally composed of Prismatic Feldspar, and straight-edged Augit of Jameson; and 7. Quartz.
The veins of Laborda and Coronas vary in dimensions from 16½ to 5½, and 8¼ English feet: that of Las Virgenes attains in some parts, a width of 27½, and even 33 English feet; nor has any diminution, or falling off, been observed at the greatest depth, to which these veins have yet been explored.
The Ores contain Native Gold, (Hexahedral Gold of Jameson,) and Native Silver, (Hexahedral Silver;) which are found in small quantities. The Rhomboidal Silverglance (l'arent antimonié sulfuré noir) is most abundant; and next to it the Hexahedral Silverglance, or Argent Sulfuré. The Red Silver, or Argent Antimonié, Sulfuré rouge, is less common, but may frequently be found.[1]
- ↑ Having professed my ignorance of Mineralogy, I must state that I am indebted for these details to a manuscript report drawn up by Mr. Burkart, Principal Miner of the Tlalpujahua Com-
