L. Diabase, east of the Sugar Loaf, Boulder County. Hessose. Description furnished by Whitman Cross. The rock contains labradorite, orthoclase, augite, and magnetite, with small amounts of hornblende, biotite, apatite, and secondary chlorite. Sp. gr., 3.027, 21°. P. R. C. 166.

M. Pyroxene separated from L.

N. Nepheline-tephrite, Elkhead Mountain, Routt County. Undescribed. Sp. gr., 2.888, 12.2°.

O. Portion of N soluble in hydrochloric acid. Recalculated to 100 per cent.

Analyses L to O made by L. G. Eakins in the Denver laboratory. Hitherto unpublished.

UTAH.

1. ROCKS FROM THE TINTIC DISTRICT.

Described by Tower and Smith in 19th Ann., Part III, pp. 609 et seq. Analyses by Stokes, record No. 1746.

A. Gray, porphyritic rhyolite, south of Pinyon Creek. Toscanose. Contains phenocrysts of sanidine, quartz, biotite, plagioclase, and hornblende; the last mineral sparingly. Also tridymite, magnetite, apatite, zircon, and a small amount of glassy residue. P. R. C. 1039. B. Quartz-porphyry, Swansea mine. Toscanose. Phenocrysts of feldspar and quartz, the orthoclase somewhat altered. Microscopie biotite occurs sparingly. Also contains magnetite, apatite, zircon, a little chlorite, and secondary pyrite. P. R. C. 1040.

C. Andesite, Tintic Mountain. Harzose. Phenocrysts of biotite and feldspar. Contains plagioclase, chiefly labradorite, augite, biotite, hypersthene, magnetite, and apatite, in a dark-gray glass. P. R. C. 1036.

D. Granular monzonite, Iron Duke mine. Harzose. Contains orthoclase, plagioclase, quartz, hornblende, biotite, magnetite, apatite, zircon, and titanite, with a little chlorite and epidote. P. R. C. 1032. E. Altered monzonite, near Tintic mine. Feldspar and ferromag nesian minerals completely altered. Rutile is present; quartz seems to have been added.

2. ROCKS FROM HENRY MOUNTAINS.

A. Porphyry. Tonalose. Not hitherto published. Reported by J. S. Diller as containing prominent plagioclase with some augite and hornblende in a crystalline groundmass of quartz and orthoclase. Analysis by R. B. Riggs, record No. 728.

B. Augite-porphyrite, dike, north spur of Mount Pennell. Laurvikose. Contains hornblende, augite, and plagioclase in a feldspathic groundmass.

C. Hornblende-porphyrite, Mount Hillers. plagioclase, hornblende, quartz, and magnetite.

Tonalose. Contains.

Rocks

Analyses B and C by W. F. Hillebrand, record No. 1428. described by Cross in 14th Ann., p. 165.

3. ROCKS FROM BINGHAM.

Porphyries collected by J. M. Boutwell, but not yet described. Analyses by E. T. Allen, record No. 1985.

A. From Tribune tunnel, Telegraph mine. Monzonose.

B, C, D. From British tunnel, Last Chance mine. B, SR. 1 of dacase. C, harzose. D, monzonose.

According to Boutwell, A is the characteristic Bingham porphyry, and is intermediate between diorite-porphyry and monzonite. It contains chiefly augite, biotite, and plagioclase, with a few grains of pyrite. B, C, and D are altered forms of this rock.

4. ROCKS FROM THE LA SAL MOUNTAINS.

Hitherto unpublished data. Petrographic descriptions by L. M. Prindle. Analyses by W. F. Hillebrand, record No. 2032.

A. Monzonite porphyry, 2 miles west of Mount Peale. Akerose. Contains phenocrysts of plagioclase, partly resorbed hornblende, and pyroxene in a groundmass of partly striated feldspar. It may contain also orthoclase and quartz. P. R. C. 1306.

B. Aegirite-granite porphyry, about 1.5 miles south of Mount Waas. Omeose-liparose. Contains quartz, feldspar, pyroxene, and iron ore. The pyroxene is probably for the most part aegirite. P. R. C. 1304.

C. Syenite-aplite porphyry resembling grorudite. About 2 miles south of Mount Waas. Liparose. Contains potash and soda-lime feldspars, quartz, pyroxene, titanite, and iron ore. In the groundmass are needles which are probably aegirite. P. R. C. 1301.

D. Syenite porphyry resembling sölvsbergite. About 1 mile northwest of Mount Waas. Phlegrose near nordmarkose. Contains potash and soda-lime feldspars, quartz, pyroxene, and iron ore. Needles of aegirite (?) in the groundmass. P. R. C. 1303.

E. Pulaskite, 1 mile west of Mount Waas. Nordmarkose. Contains potash feldspar, pyroxene, biotite, apatite, titanite, and iron ore. P. R. C. 1305.

F. Noselite-syenite porphyry, dike on northwest shoulder of Mount Waas. Miaskose. Contains feldspar, pyroxene, sodalite or noselite, apatite, titanite, and iron ore. The pyroxene appears to be mostly aegirine-augite and the feldspar mainly potash-feldspar. P. R. C.