The mineral which is the subject of this note was discovered early in this year by Mr. Hawkins and T. Edwin Sanders, who were prospecting- in the southern part of the Mt. Diablo range, near the San Benito-Fresno County line, about latitude 36Ã‚Â° 20'. If was first brought to the writer's attention by Shreve & Company, who had purchased one of the cut stones from a lapidary and who were later offered some of the rough material as sapphire. They soon determined that it was not sapphire but were unable to place it, and so sought the aid of the University. Sufficient material for the chemical analysis and for the crystallo-graphic and other determinations was kindly supplied by Mr. Hal Sanders of San Francisco, a brother of one of the original discoverers. The writer is also indebted to Professor O'Neill for the privileges of the chemical laboratory and for many courtesies.
As the progress of the investigation has shown that it is a new mineral species, it has been called benitoite, as it occurs near the head waters of the San Benito River in San Benito County.
The most striking characteristic of the mineral is its blue color, and selected crystals cut in the right direction produce a