IGNEOUS AND CRYSTALLINE ROCKS. 25 
The following rocks, D to H, are from Prospect Hill, west of Litchfield. Collected 
by W. H. Hobbs, who furnishes the petrographic data: 
D. Mica-hornblende gabbro. Bandose. Contains plagioclase, hypersthene, biotite, . 
subordinate green hornblende, and magnetite. P, R. G. 1677. 
E. Homblende diorite. #essose. Contains plagioclase, green hornblende, sub- 
ordinate biotite, and magnetite. P. R. C. 1678. 
F. Hornblendite. III. 6. 4. 4, 5. Almost entirely green hornblende. Contains 
also magnetite, a little biotite, and very little plagioclase. P.R.C. 1679. 
G. Cortlandtite. IV. 17. 17, 2. Mainly hypersthene, with subordinate olivine, 
green hornblende, and magnetite. P. R. C. 1680. 
H. Hornblende norite. Awvergnose. Contains greenish hornblende and a little 
more hypersthene. Rich in plagioclase, with accessory biotite and magnetite. P. R. 
C. 1681. 
Analyses D, G, H, by W. F. Hillebrand, record No. 2074; E and F by George Steiger, 
record No 2071. 
CUS aeqennminmtete siete eb 2h ce eae SSE : .-| trace? |... 
100.12 | 99.92 99.75 | 100.16 | 100.25 
The following rocks were collected by G. F. Loughlin. Petrographic data supplied 
by H. E. Gregory. Analyses by G. Steiger. 
I. Gabbro, near northeast boundary, between Preston and Griswold. Contains 
plagioclase, pyroxene, hornblende, epidote, zoisite, chlorite, serpentine, pyrite, 
ilmenite, apatite, and a little calcite. 
J. Quartz diorité, 1 mile east of Preston City post-office. Contains quartz, plagio- 
clase, little orthoclase, hornblende, little biotite, rare muscovite, epidote, zoisite, 
pyrite, ilmenite, apatite, and zircon. 
K. Granite dike, southern slope of Barnes Hill, North Stonington. Contains 
quartz, orthoclase, oligoclase, biotite, muscovite, titanite slightly altered to leuco- 
xene, epidote, chlorite, ilmenite, pyrite (?), zircon, andapatite. Somewhat kaolinized. 
L. Amphibolite dike, east base of Prospect Hill, northwest of Preston City post- 
office. Contains plagioclase, hornblende, epidote, ilmenite, pyrite, apatite, and a 
little kaolin and sericite. 
