E. Altered rhyolite, De Lamar mine, Silver City. Contains quartz, sericite, pyrite, apatite, and rutile, with some undeterminable magnesian mineral. Analysis by H. N. Stokes, record No. 1731.

F. Altered rhyolite, De Lamar mine. kaolinite, and pyrite. Sp. gr., 2.655, 23°.

Contains sericite, quartz,

G. Altered rhyolite, De Lamar mine. Contains quartz, sericite, kaolinite, and pyrite. Sp. gr., 2.576, 24°.

H. Diabasic basalt, Trade Dollar mine, Silver City. Camptonose. Contains labradorite, augite, chlorite, magnetite, secondary quartz, etc. Analyses F, G, and H, by Hillebrand, record No. 1826.

I. Quartz-monzonite, Schafer Butte, Boise County. Lassenose, Contains quartz, orthoclase, oligoclase, biotite, apatite, titanite, and magnetite. Analysis by George Steiger, record No. 1802.

J. Granodiorite, Silver Wreath mine, Boise County. Yellowstonose. Contains orthoclase, oligoclase, apatite, biotite, titanite, and magnetite. Described in 18th Ann., Part III, p. 642. Sp. gr., 2.714, 23°. Also described in 18th Ann.

K. Same as J, but in altered condition. Contains sericite, quartz, titanite, apatite, and pyrite, with carbonates of calcium, magnesium, and iron. Sp. gr., 2.774, 23~.

Analyses J and K by George Steiger, record No. 1691.

L. Volcanic sand, Nez Perces region. Collected by I. C. Russell. Analysis by W. F. Hillebrand, record No. 1906.

M. Typical basalt, Cinder Buttes, west side of Snake River plains. Camptonose. Analysis by W. F. Hillebrand, record No. 1950. Analysis published by Russell in Bull. 199, but the mineralogical composition of the rock is not given. Sp. gr., 2.907 at 24°.

COLORADO.

1. DENVER BASIN.

Rocks described by Cross in Mon. XXVII.

Analyses A, B, D, and E by L. G. Eakins, C by W. F. Hillebrand. All but A were made in the Denver laboratory.

A. Dolerite, dike near Valmont. Shoshonose. Contains augite, plagioclase, olivine, orthoclase, and biotite, with accessory magnetite and apatite. Record No. 1145. P. R. C. 534.

C. Basalt, Table Mountain, lower capping sheet. Shoshonose. Contains plagioclase, orthoclase, augite, magnetite, and apatite, with olivine much serpentinized. Sp. gr., 2.83, 22.5°.

D. Basalt, earlier flow, south slope of North Table Mountain. Shoshonose. Contains augite, olivine, plagioclase, probably orthoclase, magnetite, apatite, and a little biotite. P. R. C. 535.

E. Augite-mica-syenite, from north fork of Turkey Creek, Jefferson County. Shoshonose. Contains orthoclase, augite, biotite, rhombic pyroxene, hornblende, plagioclase, quartz, apatite, and magnetite. Sp. gr., 2.857, 29.5°. P. R. C. 532.

The following rocks from the Denver Basin were analyzed by L. G. Eakins in the Denver laboratory, but the analyses do not appear in the monograph. The subjoined data have been supplied by Whitman Cross.

A. Enstatite-diabase-porphyry, Mount Morrison. Bandose. Contains labradorite and enstatite in a groundmass of considerable amount, which is colorless and cryptocrystalline, probably feldspathic, and carries magnetite and other indistinct ferritic matter. P. R. C. 533. B. Augite-andesite, Table Mountain. I. 5. 3. 3. Contains plagioclase (andesine), with rare augite and biotite, in a groundmass of plagioclase, augite, magnetite, and minor accessories. This rock contained ptilolite in its vesicular equivalent. Described in Proc. Colorado Sci. Soc., 1886, p. 72.

C. Augite-andesite, a pebble from the Denver beds, Table Mountain. Yellowstonose. A few augite and andesite phenocrysts in a groundmass of oligoclase, orthoclase, and quartz (?) grains, with some augite and magnetite.

Described by E. B. Mathews. For description of A, C, E, and F see Journ. Geol., vol. 8, p. 214. Analyses by W. F. Hillebrand, record No. 1470.

A. Granitite, Sentinel Point, western part of Pikes Peak massif. Alaskose. Contains microcline, microcline-perthite, quartz, biotite, a little oligoclase, and accessory fluorite, apatite, zircon, sphene, magnetite, and allanite. P. R. C. 67 and 600.

B. Granitite, near road between Florissant and the Platte River.

Kallerudose. Consists chiefly of microcline in perthitic intergrowth with albite, quartz, and biotite. P. R. C. 606.

C. Porphyritic granitite, south side of Pikes Peak, ridge between Middle and North Beaver creeks. Liparose. Contains microcline, perthite, orthoclase, oligoclase, quartz, biotite, and accessory apatite, fluorite, zircon, and magnetite. P. R. C. 602.

D. Sheared granite, Currant Creek Canyon, north of Twelvemile Park. Magdeburgose. Contains perthitic microcline, quartz, muscovite, and sericitic aggregates replacing plagioclase and a part of the microcline. P. R. C. 604.

E. Granite, Currant Creek Canyon, north of Twelvemile Park. Omeose. Consists chiefly of perthitic microcline, quartz, greenish biotite, muscovite, and plagioclase altered to a sericitic mass. Also flakes of limonite. Accessory minerals rare. P. R. C. 603.

F. Granitite, Middle Beaver Creek, south side of Pikes Peak. Liparose. Contains microcline, orthoclase, perthitic albite, oligoclase, abundant quartz, biotite, and a little accessory magnetite, fluorite, and zircon. P. R. C. 601.

G. Granite-gneiss, north of Twin Creek. Kallerudose. Contains microcline, orthoclase, quartz, biotite, abundant fluorite, and a little sphene and apatite. P. R. C. 605.