Reézamination of American Minerals. 365 
Arr. XX XVIII —Reéramination of American Minerals : Parr 
Ul—Danburite; Carrollite; Thalite; Hudsonite ; Jenkin- 
site; Lazulite; Kyanite;.Eleolite ; Spodumene ; Petalite : 
by J. Lawrence Smirx, M.D., and Groree J. Brusu, Ph. B. 
27. Danburite. 
/ 
Tuts mineral has as yet been found in this country only at one 
locality, Danbury, Conn. It was first described by Prof. C. U. 
Shepard,* and*considered by him a hydrated silicate of lime and 
potash. Still later it was examined by Dr. H. Erni,} and boracic 
acid was found to be an important ingredient in its constitution ; 
in his analysis, however, a large amount of alkalies is indicated. 
As the results of our analyses show but a trace of these sub- 
stances and no other base but lime, it is possible that Dr. Erni’s 
alkali determination was made, through mistake, on some of the 
feldspar accompanying Danburite, as it not unfrequently happens 
that the granular portions of the feldspar resemble the lighter 
varieties of Danburite. ‘This supposition appears reasonable, as 
the silica and lime of his determinations agree with those about 
to be stated. 
The composition as given by the authorities mentioned are, 
Si ‘ * 
56°00 28:33 7 ¥?085 K(withNa?) and loss 5-12 H 8-0 =100. Shepard, 
4974 22°30 Mg 198 #eand Al211 K431 Na 982 B 924 =100. Erni. 
The results of the analyses just made, are as follows: 
3 
ke : j 4, 
11Ca, F 48°10 48:20 — — 
Alumina, 30 
Peroxyd of iron, t 1:02 cae 
Manganese, : 5) 
hit) : gies 29°41 22:33 22°22 22°11 
Magnesia, » “40 undeterm. — oe 
Boracic acid, . 27°73 27-15 — — 
Ignition, . “50 50 
00°00 99°20 
This corresponds to the following constitution, 
Pr, cts Ox. ratio. 
ti. Gli Co Se 49°42 ‘ 4 
3 2%. Borage ati bts 28-02 ‘i 3 
eee ee 22°56 1 
performing the part of a base. The formula for Danburite under 
ese views would be expressed by 
oCa Sit + Ca B? or Oa? Siz + Bs Sit 
* See Am: Jour. Sci, [1] xxxv, 129. ¢ Am. Jour. Sci. [2] ix, 286. 
