Color and Streak. The streak is the color of the powder of the mineral when rubbed on unglazed porcelain, or scratched with a knife. Transparency. Minerals may be transparent, sub-transparent, translucent, sub-translucent, opaque. Taste. Minerals may be salt, bitter, sweet, etc. Odor. This test is not of much use with most minerals until heat is applied. All the petroleum oils, however, are often detected by their odor. Chemical Composition. This may always be determined by suitable tests with reagents. Pyrognostic Characters. As a means of readily determining the nature of a specimen the blowpipe is unrivalled--if in the hands of one who understands it. Mode of occurrence and associated minerals. A knowledge of these matters often assists in a determination. A regular fire assay is not within reach of many prospectors, for the necessary apparatus cannot, as a rule, be carried in the wilderness. Whenever possible, however, a fire assay gives the truest results, especially in the case of gold and silver. [Illustration: SCALE FOR WEIGHING ORE.] The operation includes testing the ore, sampling and pulverizing, weighing the ore and reagents, calcination and roasting, reduction and fusion, distillation and sublimation, scorification and cupellation, inquartation and parting the gold and silver, weighing and tabulating. "Notes on Assaying" by Dr. Ricketts is a very useful manual to have at hand. A TOLERABLY COMPLETE OUTFIT INCLUDES: A pair of scales for weighing ore and buttons of base metal. It should take 10 ounces in each pan, and show 1/20 of a grain. A bullion scale to be kept strictly for the precious metals. Loaded with one gramme, it should show 1/20 of a milligramme. [Illustration: ASSAY BALANCE FOR BULLION.] Weights. Avoirdupois; troy, metric and "assay." Assay weights save much calculation. The unit of the system is a weight of 29.166 grammes. Its derivation is as follows: 2000 lbs. : 1 A.T. :: 1 oz. Troy : 1 milligramme. To use this system, weigh out one A.T. of the ore and whatever number of milligrammes of gold and silver the assay gives indicates an equal number of Troy ounces to the ton of 2000 lbs. Avoirdupois. A muffle and a melting furnace, portable and of medium size, are handy, though furnaces may be built of ordinary brick, lined with fire brick, that would be better for permanent use. The fuels may be coke, anthracite or bituminous coal, charcoal, oil or gas. [Illustration: ASSAY FURNACE.] [Illustration: PORTABLE ASSAY FURNACE.] Crucibles of black lead, French clay, Hessian sand, and quicklime are necessary to hold the assay. [Illustration: French Clay. Hessian. CRUCIBLES.] [Illustration: SCORIFIER] [Illustration: STEEL CUPEL MOULD.]