On halotrichite or feather alum, from Pitkin County, Colorado

E. H. S. Bailey
1891 American Journal of Science  
of Denver, 001, to the Laboratory of the State University for identification. He stated that it came from the Elk mountain range, and was found beside a ledge of "black iron ore." As no record can be found of the description or analysis of this minel al from an American 10-· cality, it has been thought that an investigation would be of value. The mineral is quite soft, has a white color, and a beautiful silky luster, resembling that of satin spar. Under the microscope and, to a certain extent,
more » ... a certain extent, by unaided vision, the mineral appears to consist of capillary crystals arranged in parallel bundles. In some places the crystals, when viewed from the end, are of a green or copperas color. Under the microscope there appear to be attached to some of the fibers minute black particles. In picking the ll1ineml for analysis these specks were eliminated as far as possible. There is only a. slight tendency towards oxidation on the sm·face; and where this occurs the mineml is yellowish red. The mineral is nearly all readily soluble in water and has a slightly acid, and very astl'ingent taste.' It fuses easily in the flame of a candle in its water of crystallization, and as the temperature increases it boils and finally leaves a reddish mass. If, however, the mineral be heated very gradually in a paraffin bath it does ]lOt melt or lose its form, but gradually loses its water. Afterwards, if heated nearly to redness, it retains its form, but gradually changes to a red color. As it was noticed that much of the water was given off at a very low temperature, a quantity of the mineral was heated below 100° 0., and, in fact, till just before the close of the experiment, below 85°, and the water thus driven off was· collected in a calcium chloride tube and weighed. The mass· was th~lS heated till no more water was given off at this temperature. 33·10 per cent of water was thus eliminated. The remainder of the water was driven off at a much higher temperature; very little, in fact, going off below 250 0 0. As the mineral was not completely soluble in water and hydrochloric acid, the solution waR evaporated to dryness and silica separated as usual. This silica, or an insoluble silicate,. is probably not a proper constituent of the mineral, but so· closely associated with it that even in the cleanest and most silky fibers it cannot be separated mechanically. The blowpipe reactions for iron are obtained. If the silky fibers be
doi:10.2475/ajs.s3-41.244.296 fatcat:iz2czqu7znamhl6vekz6cwj7sy