Page 13 - The Geology and Ore Deposits of Sierra County, New Mexico - Bulletin 10

12 GEOLOGY AND ORE DEPOSITS OF SIERRA CO., N. M.
tific aspects of the geology of the county have been minimized, and the evidence gathered in the field, as shown by surface out- crops and the portions of veins exposed underground, has been emphasized.
Throughout Sierra County, most of the small properties and many of the larger ones have been inactive for many years, and their workings have caved and have become inaccessible. Many of the owners, as well as others who were once familiar with these old workings, are no longer in the county, and the claims have declined until claim and location monuments, and the notices that were once in them, can no longer be found in the field. Where old records of production are still available or reports by reputable engineers have been read, it has been pos- sible in a measure to picture the conditions that existed in the veins when these old mines were active, but on the whole, the details of production and the value of the ore shipped have be- come clouded and in many instances are quite out of line with the evidence obtainable at surface. It is not contemplated by the State Bureau of Mines that much actual sampling of the veins shall be done by the geologist investigating ore deposits in the State for Bureau publications, and he is constrained to gather the figures as to the value of the ore from whatever source is available, and to use proper judgment in utilizing them.
In those camps now active, most of the smaller holdings have operated in the past two or three years under a whole series of new claim and company names, and the original and often historic names have been lost sight of completely. Only the more important properties, as the Rattlesnake, Bonanza, Lady Frank- lin, Silver Monument, U. S. Treasury and several others, have" held to their original names. The report has been prepared very largely on the evidence found on surface, secured without regard for property lines, and supplemented by the study of practically all of the openings accessible to the writer during his several visits to the county.
The first part of the report includes a description of the rocks and the geological history of the county, a discussion of the ore bodies and their mineralogy, and a brief review of practical points involved in the search for ore and the economical exploita- tion of this mineral wealth. The second part is given to a de- tailed description of the vein systems and other modes of occur- rence of the ore in each of the mining districts within the county, and to the descriptions of most of the mines that were open at the time of visit, and which contributed something to the store of knowledge regarding these veins.
While the material of this bulletin may be regarded as a basis on which to locate and plan future work in the ore deposits of the region, such work should not be prosecuted over long periods of time except under sound technical direction. In the long run it is always the most economical procedure to secure