DUMORTIERITE. 
By Waldemar T. Schaller. 
INTRODUCTION. 
Dumortierite was discovered by Gonnard a in November, 1879, at 
Chaponost, near Lyons, France, and was made the subject of a brief 
note by E. Bertrand in 1880. The following" year, Gonnard named the 
mineral after Eugene Dumortier, the eminent French paleontologist. 
The mineral was known to be new from its optical properties 
before its chemical composition was determined, its beautiful pleoch- 
roism being- especially marked. Damour soon after made an analysis 
of the mineral, from which he obtained the formula 4 A1 2 3 , 3 Si0 2 . 
Specimens of this mineral from New York, previously taken for 
indicolite, were studied by Diller and Riggs and shown to be differ- 
ent from tourmaline. At about the same time dumortierite from Ari- 
zona became known, and analyses of the mineral from both localities 
were made. These analyses all showed the presence of boric acid in 
varying amounts, and also a small quantity of water. An occurrence 
[of dumortierite in Norway was afterward noted, and still later several 
localities in Germany were mentioned. 
In 1902, Ford published three analyses of dumortierite, one on 
material from New York, a second on material from Arizona, and a 
third on material from a new locality in San Diego County, Cal. In 
Ehe same paper he mentions a second new locality, the fourth one in 
his country, in Skamania County, Wash. He showed by his analyses 
that dumortierite contains boric acid and water in nearly constant 
kmount. 
A careful search for crystals was made in a large quantity of the 
California mineral, which resulted in the finding of two small, imper- 
fect but measurable examples. On looking over the Arizona material 
n the National Museum a third crystal was found. Three crystals 
^ere also obtained among specimens from New York. These were 
arefully measured and some ciystallographic data were thus obtained. 
The mineral is usually sparingly present in small fibrous masses 
ttered through the rock, making it difficult to obtain an} 7 consider- 
ed For references see Literature, pp. 119-120, this bulletin. 
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