This is a variety of mica in small crystals, of a dark brown color, and quite plentiful in the gneiss inclosing the veins of limestone.

It is made of a combination of solid lubricant and ground or pulverized mica, that is where it gets its name, and nothing can equal mica as a lubricant if you could apply it to your gear; and to do this it has been combined with a heavy grease.

Dr. Hooke had succeeded in splitting a mineral substance called mica into films of such extreme thinness as to give brilliant colours.

And a few appeared embossed with wounds, covered with black mercurial hog lard, with green unguents of belladonna smeared with grains of dust and the yellow micas of iodoforme.