Aside from these general condderations bearing on its chemical character, the symmetry and physical constants of benitoite do not appear to the writer to indicate any close relation to beryl.

Benitoite forms a beautiful gem stone, but only a small proportion of the crystals are suitable for cutting. It is generally cut as a brilliant to bring out both its color and the brilliancy and fire due to its high refractive power. The deep violet-tinted blue of the finer stones is very attractive and by many it is considered more beautiful than that of the sapphire, which it distinctly surpasses in fire and brilliancy. The color varies from colorless to very deep blue, the two extremes being the least common. The finest stones are those with a moderately deep color. Considerable judgment has to be used in getting the proper attitude and proportions to bring out the full color-value while preserving the brilliancy. Both color and brilliancy vary materially in different directions and the color is often distributed unevenly or zonally. Quite a number of stones which have been cut by various lapidaries do scant justice to the possibilities of the gem. A common result is the production of a sort of dull leaden, or in the darker varieties blackish appearance.

The large stones have a general run from a carat and a half to about two carats, only a few exceeding the latter value. The largest flawless gem yet obtained weighed a little over seven and a half carats when first cut, though it has since been repolished and brought down to a little below this value. It has a moderately deep blue color and is about 14.5 mm. long, 10.5 mm. wide at the girdle, and 8 mm. deep. It is the property of Mr. G. Eacret of San Francisco. This stone is remarkable in that it is about three times as heavy as the nest largest flawless stone so far obtained, and also that it was found in the early days of the mine almost at the surface. It is shown actual size in plate 33, figures 14.

[ Images of the gem][ Articles][ Maps][ The mine]