Page:Popular Science Monthly Volume 21.djvu/365

Rh mud which held only scattered crystals without any such richness as its enveloped pocket.

Going deeper, the crystals became constantly larger, though less numerous, as the mud grew more dense, until a stratum was reached which was designated "blue clay." In the mud immediately above the blue clay, crystals from one to two inches long were very common, though many of the smaller ones were still intermingled. Here a change in the crystals showed itself, full as well marked as the change in the bed in which they lay. The small crystals were not present; they had never been formed as in the mud above. Instead of them lay imbedded scattered crystals, few in number, but of great size, and having commonly a family look by which they could be recognized. Few of them were as small as two inches in length, and not unfrequently those weighing a pound each were obtained, being perhaps five to seven inches long, by two to four inches wide.

They lay imbedded in the clay, which was so firm that they could be picked out singly, each leaving the sharp mold which it had formed during its slow process of crystallization. They were all within a little more than a foot of the surface of the blue clay, many explorations showing that it was useless to seek for them at a greater depth.

Of the abundance of the crystals within the portion of the lake occupied by them, a space of about forty acres, some idea may be formed from the fact that nine hundred pounds have been gathered from one dam, four feet square. And this by no means represents their full amount, as all the smaller crystals were washed back again into the lake in the process of their separation. At the same time it was remarkably true that the yield was very uneven. In what was known as "rich ground" barren spots constantly occurred, and often almost the entire yield of a dam came from one side or one corner, perhaps only a third or a fourth part of the full area.

The crystals thus obtained had a decidedly green color. The figure introduced is given for the purpose of conveying an idea of the size which the green crystals sometimes attained. It is not an exaggeration. I have seen many which weighed individually as much as the one here delineated. Their proportions were very erratic, but always conforming to the one type.

They were entirely free from the tenacious coating incident to the tincal of other localities; were readily and perfectly soluble in hot water, and in the process of refining by solution and recrystallization yielded-their full weight of transparent borax of the finest quality, less merely the weight of the mud which had been mechanically entangled with them during their growth in a muddy menstruum. The green color disappeared in the refining, not being found either in the deposited mud or the new crystals.

We are prepared now to look at the origin of these salts as held in solution or in crystalline form. If, in a basin of water, more or less