Copyright © 2004 by Ana Minerva Bonilla                                            Updated: 7/22/05 15:00

The Weekend Miner

(http://theweekendminer.com)

California

Inyo County

Darwin Mining District : (Lead, Zinc, Silver, Tungsten, Antimony and Copper)

Mines Identified in the District;

Cerro Gordo Mine                                                                             

Christmas Gift Mine                                                                             

Custer Mine                                                                                            

Darwin Antimony Mine                                                                        

Darwin Mine                                                                                           

Defiance Mine                                                                                        

Durham-Fernando Mine                                                                          

Empress Mine                                                                                         

Lucky Lucy Mine                                                                             

Silver Spoon Mine                                                                             

St. Charles Mine       

Thompson Mine                                                                                                                              

Description(s) of the District;

The Darwin Mining District is located at 36.17N by 117.35W and is known for deposits of lead-silver-zinc ore, including several rare sulfosalts. Also found are ores of tungsten, antimony and copper. Gold was also produced from a number of mines in the area, both as a primary and by product.

The geology of the area was described by Hall and MacKevett in 1958 and Hall again in 1962, as follows: Lead-zinc-copper ores occur in a sequence of upper Paleozoic sedimentary rocks ranging in age from early Ordovician to Permain. These sedimentary rocks were intruded by a biotite-horneblende quartz monozonite stock of Jurassic age and were altered to calcite-silicate minerals. Ore deposits are correlated with the lower member of the Keeler Canyon formation, which is of Pennsylvanian and Permian age. Overturned bedding in the meta-sedimentary rocks strikes N. 30° and dips 50° SW, with many faults cutting these rocks at steep angles.

Most of the ore mined from the Darwin District is massive and occurs in veins, bedded deposits and steep, irregular replacement-type bodies. The sulfide ore consisted of galena, sphalerite, and pyrite, with lesser amounts of bismuthinite (Bi 2 S 3 ), chalcopyrite, arsenopyrite, pyrrhotite, stibnite, tetrahedrite, and rare Ag-Cu-Pb-Bi sulfosalts; some of which contain Se substituting for S. Oxidation of the sulfide ore has produced massive cerussite (PbCO 3 ), with lesser amounts of malachite, azurite [Cu3(CO3)2(OH)2], aurichalcite, chrysocolla, smithsonite, hemimorphite [Zn4Si2O7(OH)2-H2O] and hydrozincite.