7. HIGHWOOD MOUNTAINS.

Rocks collected by W. H. Weed and L. V. Pirsson, who furnish the petrographic data. Analyses A to N, inclusive, made in the laboratory of the Sheffield Scientific School, under the direction of Professor Pirsson.

A. Trachy-andesitic breccia, head of north fork of Willow Creek. Adamellose. Contains hornblende, biotite, iron ore, apatite, plagioclase, and orthoclase, with a little kaolin and limonite. E. B. Hurlbut and B. Barnes, analysts.

B. Trachyte, dike 1 mile north of divide in Highwood Gap. Highwoodose. Contains abundant phenocrysts of orthoclase and augite in a groundmass of the same minerals; also a little biotite, apatite, and iron ore, and some secondary kaolin. E. B. Hurlbut, analyst.

C. Trachyte, dike north end of South Mountain. Pulaskose. Contains phenocrysts of alkali feldspar, ægirine-augite, and melanite, in a groundmass of alkali feldspar. Apatite, iron ore, a trace of calcite, and some kaolin are also present. H. W. Foote, analyst.

D. Trachyte, dike on Aspen Creek. Monzonose. Contains alkalihornblende and alkali-feldspar phenocrysts, in a groundmass of alkali feldspars; also some apatite and iron ore. Rock stained by limonite. H. W. Foote, analyst.

E. Trachyte, dike at head of Shonkin Creek. Judithose. Contains augite, biotite, iron ore, and orthoclase, in a groundmass of alkali feldspar; also apatite and some kaolin. W. M. Bradley, analyst.

F. Syenite, top of Palisade Butte. Borolanose. Contains augite, iron ore, apatite, alkali feldspar, a little biotite, some limonite in cracks, much natrolite, and possibly other zeolites. H. W. Foote, analyst.

G. Leucite-syenite, head of Davis Creek. Shonkinose. Contains augite, iron ore, olivine, biotite, apatite, alkali feldspar, leucite, and some zeolites, with traces of limonite and serpentine. E. B. Hurlbut, analyst.

H. Monchiquite, dike east side of Highwood Gap. Monchiquose. Contains augite, olivine, biotite, iron ore, apatite, and analcite, with some serpentine and a little kaolin. H. W. Foote, analyst.

I. Leucite-basalt, saddle between Highwood and Pinewood peaks. Shonkinose. Contains augite, iron ore, leucite, apatite, altered olivine, chlorite, calcite, and zeolites. H. W. Foote, analyst.

J. Leucite-basalt or leucite-monchiquite, dike on Arrow Peak. Near kamerunose. Phenocrysts of augite, olivine, and biotite, with some leucite, in a groundmass of the same minerals. Also analcite, iron ore, and apatite. H. W. Foote, analyst.

K. Missourite, head of Shonkin Creek. Near belcherose. Described in Amer. Journ. Sci., 4th series, vol. 2, p. 315. Contains apatite, iron ore, olivine, biotite, augite, and leucite, the two latter being the chief minerals. Some zeolites and analcite are also present. E. B. Hurlbut, analyst. P. R. C. 356.

L. Pseudo leucite-syenite, head of Shonkin Creek. Fergusose. Contains augite, olivine, biotite, iron ore, apatite, orthoclase, nephelite, zeolites, and traces of serpentine, limonite, and kaolin. Contains pseudomorphs after leucite. E. B. Hurlbut, analyst.

M. Monzonite, Highwood Peak. Shoshonose. Contains augite, biotite, iron ore, apatite, plagioclase, and alkali feldspar. E. B. Hurlbut, analyst.

N. Monzonite, Middle Peak. Borolanose. Contains augite, olivine, biotite, iron ore, apatite, plagioclase, and orthoclase. The two latter, with augite, are the chief minerals. E. B. Hurlbut, analyst.

O. White syenite of the Shonkin Sag laccolith. Partial analysis. P. Shonkinite, Shonkin Sag laccolith. Contains augite, olivine, biotite, and orthoclase.

Rocks O, P, described by Weed and Pirsson in Amer. Journ. Sci., 4th series, vol. 12, p. 1. Analyses by W. F. Hillebrand, record No. 1885.

The following rock and separations, from Square Butte, at the east end of the Highwood Mountains, are described by Lindgren in Amer. Journ. Sci., 3d series, vol. 45, p. 286. Analyses by W. H. Melville, record No. 1268.

A. Post-Cretaceous sodalite-syenite. Pulaskose. Contains orthoclase, some albite, hornblende, sodalite, analcite, and apatite. Orthoclase predominates. The sodalite amounts to 8 per cent. P. R. C. 184 and 201.

B. Hornblende separated from A. Near barkevikite.

In addition, the orthoclase gave 3.88 per cent Na,O and 11.03 per cent K,O. A separation of mixed feldspars (sp. gr., 2.56) gave 6.08 per cent Na, and 8.91 per cent KO.

Granite-syenite-porphyry. Liparose. Described by Weed and Pirsson, Journal of Geology, vol. 4, p. 399. Contains orthoclase, quartz, oligoclase, iron oxides, and a little muscovite. Analysis by H. N. Stokes, record No. 1558. P. R. C. 905.