The Forrest City times., 1896-01-17
TESTING THE ORES.
How Samples from the Diggings Are Prcs
 pared for the Assay Omce.

 pared for the Assay Omce.
 | To the uninitiated but observant stranger who wanders up and down in the labyrinth of shafts and tunnels, diggings and dumps of genuine min- ing camp perhaps there is no subject more full of interest than the process by which a lump of brown ore, which, to his inexperienced eye, looks not in the least attractive, is made to yield its share of silver and gold, or the means and methods by which the min- ing man at his side so confidently as- sures him that a ton of that ore will go S2.33 ounces in silver and S17.55 in gold. Even the easter n mining expert or graduate from some mining school will wonder how, in the log cabin or pine shanty, destitute of all the elab- crate paraphernalia 10 which he has been accustomed, these results are so readily and accurately obtained.
 As general rule the majority of the ores, except those containing the pre- | cious metals, for purposes of purchase and sale are valued according to the cost of mining and shipping, so tbat, ex- cept for metallurgical purposes, His un- necessary to seek to determine with much accuracy the contents and value. of such ores. In case of ores rich in the precious metals. however. it is en- tirely different, as in their purchase and sale both parties, the buyer as we'll as the seller, want to ascertain ac- curately and to a certainty the value of the entire lot. The methods by which this knowledge is obtained are so simple as to be easily understood and practiced by many man who does not know the technical symbols of the metals he is determining or could not give a scientific exposition of the proc ess, but, nevertheless, in his line, he | is an accurate and successful assayer When quantity of ore is to be sam | pied for assaying it is first broken by an ordinary rock crusher into pieces the size of an English walnut, after which it is shoveled back into the car, but in such manner that every fifth shovelful is thrown aside by itself, the remaining four-ffths being finally taken away This fifth portion, known as the 'sample,' is then reduced to much greater degree of fneness by means of Cornish rolls. It is then piled on the floor in cone, flattened out, and divided into four equal portions, and two opposite quarters are then removed. The remaining quarters Ire again thoroughly mixed and again piled in a cone, fattened and quartered; this operation being repeated until the sam pie is reduced to 100 pounds. It is then weighed repeatedly for the purpose of determining the amount of moisture contained in the ore, which in some ores, especially those of the concen- trates, is so considerable as to make very appreciable difference in the weight. The moisture is then expelled and the orc is crushed to such degree of fineness that it can be passed through a sieve containing 100 holes to the linear inch. The sample is next put up in small bottles, which are sealed with sealing wax and then stamped for the purpose of preventing the possibility of their being opened or tampered with without detection.
 The above is the process of sampling used among the mines, and the sam pie is now ready to be assayed but only a small portion of it will be used for that purpose, and the quantity gen. orally taken is what is known as an assay ton," which weighs 29, ,166 milli- grams, or little more than 450 grains troy weight. This definite amount is taken, partly as a matter of conven- fence, and also because the assayer wishes to ascertain, as quickly as possi- ble, how many ounces of the precious metals to the ton are contained in this ore. The method used depends upon the following principle: The avoirdu- pois grams ton of 2,000 pounds contains 20, ,166 ounces troy weight; hence, when l 29,166 milligrams of the unassayed ore are taken, the weight of the resulting | button" of gold or silver in the milli- grams represents at once, without any further calculation, the number of troy ounces of gold or silver in the avoirdu. | pois ton of the ore.
 This method was invented in the 1 Columbia School of Mines in New York city and is in general use throughout | the world wherever there is assaying to be done.--Boston Transcript.
 Fully Explained.