Franklinite, a zinc-manganese ore, is also a common source of supply. An ore to be commercially valuable should contain from 40 to 60 per cent. metallic manganese, and not over 0.2 to 0.25 per cent. phosphorus. To determine the value of manganese ores a somewhat intricate calculation is necessary. Delivered at Bessemer, Pa., the Carnegie Steel Company pays according to the following sliding scale: Per cent. Mn. Per Unit over 49 p.c. Fe. Mn. 46 49 p.c. 6c 28c 43 46 p.c. 6c 27c 40 43 p.c. 6c 26c 37 40 p.c. 6c 25c 34 37 p.c. 6c 24c 31 34 p.c. 6c 23c 6c 22c Moreover, for each one per cent. of silica in excess of eight per cent. a deduction of fifteen cents a ton is made, and a deduction of one cent per unit of manganese is made for each 2/100 of one per cent. of phosphorous present in excess of 1/10 per cent. From which it is evident that there can be little profit in impure deposits of manganese. Mercury. Quicksilver usually occurs in the form of cinnabar, though occasional deposits of pure metal are found in drops and small pockets, in limestone and the softer secondary rocks, including shales and slates. As the appearance of quicksilver must be familiar to all, cinnabar alone needs description. Its specific gravity is 9.0; its hardness, 2.2. It is a red brown earthy ore, the powder of which is a dull red. It is generally found in sandstone, though it occasionally occurs in slates, shales and serpentine. Heated gently with lime cinnabar yields quicksilver. If copper be held over the fumes of mercury it will be coated with a light film of the metal. An alloy with silver has been found. Mercury is heavy, extremely brilliant, and mobile. The composition of cinnabar is: Per cent. Hg. Cinnabar HgS 86.2 Although but three American states have supplied this metal, this country has held rank as second producer. Of these California is by far the most important. Oregon and Utah having never had any but a small and spasmodic output. Judging by Californian experience, the prospector is most likely to find cinnabar, the ore from which the quicksilver of commerce is derived, in metamorphic rocks. Mercury is always sold in flasks of 76-1/2 pounds. The production of mercury by the United States (California) was 28,879 flasks in 1899, which were valued at $1,155,160. The following table shows the rock in which the most famous Californian quicksilver mines are: