8/13/2019 Tests for Metal Ores

1/3

Gold:A test known as Darton's is believed to be a valuable means of detecting minutequantities ofgoldin rocks, ore tailings, etc. "Small parts are chipped from all the sides of amass of rock, amounting in all to about | ounce. This is powdered in a steel mortar and wellmixed. About half is placed in a capacious test tube, and then the tube is partly filled with asolution made by dissolving 20 gr. of iodine and 30 gr. of iodide of potassium, in about 10

ounces water. The mixture thus formed is shaken and warmed. After all particles havesubsided, dip a piece of fine White filter paper in it; allow it to remain for a moment ; then letit drain, and dry it over the spirit lamp. It is next placed upon a piece of platinum foil held ina pincers, and heated to redness over the flame. The paper is speedily consumed; and afteragain heating to burn off all carbon, it is allowed to cool and is then examined. If at all

purple, gold is present in the ore, and the relative amount may be approximately deduced.This method takes little time, and is trustworthy."

Copper:Copper is a very easy mineral to test for. First crush the ore and dissolve it in nitricacid by heating. Then dilute with some water, and add ammonia. The solution should turndark blue. The carbonate ores of copper do not extend deep in the mine. Their places are

taken by copper pyrites. Sulfide ores are usually difficult to treat, and when they are to betested it is better to roast them before trying the tests for color. Test for copper may also bemade as follows: The sample must be pulverized. Take an ounce of the powder, and place ina porcelain cup. Add forty drops of nitric acid, twenty drops of sulfuric acid and twelve dropsof hydrochloric acid. Boil over the spirit lamp until white fumes arise. When cool, mix with alittle water. Filter and add a nail or two to the liquid. The copper will be precipitated, andmay be gathered up and weighed. The amount of copper in the sample multiplied by 32,000will be the copper in a ton of the ore. Should copper be suspected, roast the powdered ore andmix with an equal quantity of salt and candle grease or other fat; then cast into the fire, andthe characteristic flame of copper first blue and then green will appear. This test is bettermade at night.

Mercury:.Cinnabar,the common ore of mercury, is a sulfide. Scratch it with a knife, andthe streak will be bright crimson. Dissolve the ore in nitric acid, add a solution of caustic

potash, and you have a yellow precipitate. A very pretty test is to place the ore pulverized in aglass tube with some chloride of lime; close the top of the tube, and place a smaller onetherein, so bent that it will pass into a basin of water; heat the bottom of the tube containingthe ore and lime, keeping the upper part and the small tube cold with wet rags, and you willhave a deposit of quicksilver in the basin.

Silver:silver oresmay be detected by dissolving a small quantity in a test tube with a few

drops of nitric acid. Boil until all the red fumes disappear. Let the solution cool, and add alittle water. Filter the whole, and add a few drops of muriatic acid, which will precipitate thewhite chloride of silver. Dissolve this precipitate with ammonia; then add nitric acid oncemore. Exposed to the light, the precipitate soon shows a violet tint. Pure silver is the brightestof metals, of a brilliant white hue, with rich luster. To detect chloride of silver in a pulp, rubharshly with a clean, bright and wet copper cartridge or coin, and if there be silver in the pulpthe copper will be coated with it. Graphite will also whiten copper, but the film is easilyrubbed off.

Nickel:Nickel may be determined as follows: A little of the powdered ore taken up on thepoint of a penknife, and dissolved in a mixture of ten drops of nitric and five drops of

muriatic acid, should be boiled over a lamp for a few minutes, and ten or twelve drops of

http://nevada-outback-gems.com/mineral_information/gold_mineral_info.htmhttp://nevada-outback-gems.com/mineral_information/gold_mineral_info.htmhttp://nevada-outback-gems.com/mineral_information/gold_mineral_info.htmhttp://nevada-outback-gems.com/mineral_information/cinnabar_mineral_info.htmhttp://nevada-outback-gems.com/mineral_information/cinnabar_mineral_info.htmhttp://nevada-outback-gems.com/mineral_information/cinnabar_mineral_info.htmhttp://nevada-outback-gems.com/prospect/gold_specimen/Silver_ores.htmhttp://nevada-outback-gems.com/prospect/gold_specimen/Silver_ores.htmhttp://nevada-outback-gems.com/prospect/gold_specimen/Silver_ores.htmhttp://nevada-outback-gems.com/prospect/gold_specimen/Silver_ores.htmhttp://nevada-outback-gems.com/mineral_information/cinnabar_mineral_info.htmhttp://nevada-outback-gems.com/mineral_information/gold_mineral_info.htm

8/13/2019 Tests for Metal Ores

2/3

8/13/2019 Tests for Metal Ores

3/3

dipping it into water. Some metal comes to the surface in a greasy scum, should silver bepresent. Native silver is found occasionally. Owing to the fall in value of this metal its futureis not assured. It has fallen, during the past year, once to forty-nine cents an ounce, and thishas had a most disastrous effect upon many silver mines, forcing them to suspend operations.Should the fall continue, as seems likely, and the price of silver go down to forty cents an

ounce, little will be produced except as a by-product in the treatment of argentiferous leadores.

As silver enters into chemical combination with sulfur easily, as is seen by the black film thatforms on silver articles in a room where gas is burnt, most silver oresaresulfides.The veryabundance of silver has caused its great fall in value, and it does not appear that it is everlikely to remain for long at a price exceeding fifty cents an ounce, owing to the ease withwhich it may be produced, and the large quantities that must find their way to market throughit being a by-product in lead smelting. From 1859 to 1891 the Comstock lode in Nevada

produced $325,000,000. This lode is a belt ofquartz,10,000 feet long and several hundredwide, and is a contact vein between diorite and diabase. In Americagalenais the principal

source of silver; the chlorides and oxides rank next; while, lastly, some silver is parted fromgold when it reaches the mint, as gold always contains more or less of that metal. No precisestatement as to the manner of its occurrence may be made since it is found in many different

positions, and is associated with all sorts of minerals. It is never found in placer deposits, as itbreaks up under the influence of water, air, etc. Its original source is doubtless the igneousrocks, where it occurs in association with augite, hornblende and mica.

http://nevada-outback-gems.com/prospect/gold_specimen/Silver_ores.htmhttp://nevada-outback-gems.com/prospect/gold_specimen/Silver_ores.htmhttp://nevada-outback-gems.com/prospect/gold_specimen/Silver_ores.htmhttp://nevada-outback-gems.com/Reference_pages/sulfide_ores.htmhttp://nevada-outback-gems.com/Reference_pages/sulfide_ores.htmhttp://nevada-outback-gems.com/Reference_pages/sulfide_ores.htmhttp://nevada-outback-gems.com/mineral_information/Quartz_mineral_info.htmhttp://nevada-outback-gems.com/mineral_information/Quartz_mineral_info.htmhttp://nevada-outback-gems.com/mineral_information/Quartz_mineral_info.htmhttp://nevada-outback-gems.com/mineral_information/galena_mineral_info.htmhttp://nevada-outback-gems.com/mineral_information/galena_mineral_info.htmhttp://nevada-outback-gems.com/mineral_information/galena_mineral_info.htmhttp://nevada-outback-gems.com/mineral_information/galena_mineral_info.htmhttp://nevada-outback-gems.com/mineral_information/Quartz_mineral_info.htmhttp://nevada-outback-gems.com/Reference_pages/sulfide_ores.htmhttp://nevada-outback-gems.com/prospect/gold_specimen/Silver_ores.htm