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 76½ 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:
| Mine. | County. | Rock. |
| Sulphur Creek | Colusa | Serpentine. |
| Abbott | Lake | Shale-serpentine. |
| Great Western | Lake | Serpentine. (?) |
| Ætna | Napa | Sandstone. |
| Corona | Napa | Sandstone-serpentine. |
| Aat Hill | Napa | Sandstone. |
| New Almaden | Santa Clara | Shale-serpentine. |
| Barton | Siskiyou | Shale-sandstone. |
| Cinnabar King | Sonoma | Sandstone-serpentine. |
| Altoona | Trinity | Porphyry-serpentine. |
A study of the foregoing shows that serpentine is almost as intimately connected with quicksilver as is quartz with gold, or granite with tin. These are the things that prospectors should make a note of. With the great increase of gold mining and the limited store of cinnabar that is available that ore seems certain to rise in value before long.
Mica. The value of Indian mica varies from 90¢ a pound for sheets 4 in. × 1 in. to $13 a pound for sheets 10 in. × 8 in. The white mica in large sheets is valuable. The amber-colored, and spotted, are used for insulating purposes in electric plants, while the coarser sorts are ground and used as lubricants, or in fire-proof paint manufacture.