a 
flrs paper the equivalent of SiOz, has 
T. S. Hunt on Euphotide and Saussurite. 341 
The oxygen ratios of the alkalies and alumina in the above 
aualysis are very nearly as 1:8, and if to these we add the 
silica corresponding to twelve equivalents, or in round numbers 
to 24:00 of oxygen (equal to 45-00 of silica) we shall have 65°78 
parts of albite, in which the oxygen ratios are1:3:12. The | 
oxygen of the remaining silica and protoxyds equal 9°81 : 4-48, 
showing a slight excess of silica over the proportion required to 
orm a pyroxene, 
The feldspathic base of dioritic and doleritic rocks is some- 
limes eveh more silicious than albite, and passes into petrosilex, 
which may be regarded as 
perhaps a distinct feldspar like krablite. Brongniart mentions 
trosilex as sometimes forming the base of euphotide, and 
des alumina, lime, magnesia and oxyd of iron. In this con- 
nection I may ci 
8s of two varieties of petrosilex. The first (4) forms great 
i nt] 
ser conchoidal fracture; it is distinguished from the diorites 
. escribed by the absence of the white opaque coating upon 
0) , dull, Hardness 6:0; density 2°635—2°639. 
from St. Henri, is a finely granular greenish rock, which 
ie iit Strata which are regarded as the equivalents of the 
wag Series, It is somewhat less compact and tenacious than 
» which however, it closely resembles. 
a. Ei virvnaed in: 1840... +005 71:40 
ES A icine is eka yg 116) ..4ss.- 13:60 
Sa Vet epee GL. 3:31 
nau blest TeeC ene 198 ists 2:37 
gad a eatin Bh baie es 84 
pagnesia, Pee isis Vi aksanes 2°40 
RG, ec ee | Sees 3°24 
Be nee ee 9 2°50 
4 Wh: 79 99°66 
rocks . a ¢ engaged in the examination of the various feldspathic 
neta are associated with the ophiolites of Canada, I was 
gray; looking for some mineral nite hardness and specific 
oe 'Y should correspond to those of the jade or saussurite of 
tT - See for further anal . 
58, in which yses the Report of Geol. S f Canada for 1856, ps 
ma lh oe above analysis is calculated for ha ‘old equivalent weights 2 
» * 
