- 
472 R. C. Hills— Kaolinite from Colorado. 
A,+A 
As A, and A, are constants, let us put Ee Sa A, and 
Ds A _ al; the at ions then become 
a oe the above equations then become 
P tg +7 
i cos (A, — P)=5 ae a’ 
Sout A eke ti 
x ean ae é 
from which ¢ and VY are easily found. The most favorable values 
of A, and A,, give A,— A,=+ 90°. The angle ¥’ should (in 
order to use the formule already given for Ja and Jz) be taken 
in the quadrant of greatest temperature; then in order that ¢ may 
always be considered positive we substitute, as before, the value 
180° + W’ in the equations for Ja and 4z. The argument D can 
be found by means of table I from the expression ai=a >. 
D 
Ann Arbor, April 12, 1884. 
Arr. LVII.—Kaolinite, from Red Mountain, Colorado; by 
| CHARD C. HILLS. 
AT a recent meeting of the Colorado Scientific Society, Mr. 
~Whitman Cross called attention to an interesting variety of 
kaolinite found by the writer in the National Belle mine at 
Red Mountain, Ouray County, Colorado. 
e€ appearance of the mineral in question is that of a mass 
of small glistening white scales visible to the naked eye. UN 
der the microscope these scales are resolved into remarkably 
perfect transparent crystals, all of which differ from those hith- 
erto described under the head of kaolinite in the development 
of well-defined pyramidal planes, to the exclusion, in most In- 
stances, of those m the prismatic zone. The general form !s 
shown in the annexed diagram, which is a camera lucida draw- 
ing of three of the observed crystals. 
The mineral occurs in considerable quantities, associated with 
galena and its oxidation products, in the huge vuggs, or cham- 
bers lined with ore, found irregularly distributed through an 
se mass of quartz, the latter being enclosed in a highly 
im 
 kaolinized rock of eruptive origin. 
