IGNEOUS AND CRYSTALLINE ROCKS. , 83 
Vv. Theralite, Gordons Butte. Malignose. Contains green augite, egirine, biotite, 
olivine, nephelite, sodalite, and a feldspar, partly sanidine, containing K, Na, Ba, Sr, 
and Ca; also accessory apatite, magnetite, and sphene. 
W. Theralite, Gordons Butte; another sample. Aanuerunose. Analysis by E. A. 
Schneider, record No. 1281. P. R. (. 75. 
X. Theralite, north of Alabaugh Creek. Essexose. Described by Wolff for the 
Educational Series (Bull. 150). Contains augite, xgirine, biotite, olivine, magnetite, 
apatite, nephelite partly zeolitized, a mineral of the sodalite group, sanidine, and 
analcite. Analysis by Schneider, No. 1281. P. R.C. 76. 
Rocks V, W, and X are described by Wolff in Bull. 150, pp. 197, 199. 
Y. Altered theralite, head of Shields River, west of Loco Mountain. Received 
from W. H. Weed. Analysis by H. N. Stokes, record No. 1547. 
Z. Hornblende picrite, Conical Peak. Auvergnose. Datasupplied by J. P. Iddings. 
Contains hornblende, plagioclase, hypersthene, augite, olivine, very little primary 
quartz, and probably some magnetite and apatite. Analysis by L. . Eakins, record 
No. 1379. 
y W 5G, Y Z 
2a3 t 
Bie: soce5 Ye potenne Mh seceetos vere she) By wee aeser PERSE 48. 90 45.71 
SANGO) 9 dec seco eh Lepsceier el vacssonsiane nis Semeana alas aanesels Secgeaaie hse baste SST eyeinseos 14.70 10. 80 
MEG 3 Osh os dar cecsts his astec atgis Sarasa cde Ne MUM ua eid teh Sara otra tisaabe weenie 4.14 4. 43 
BGO ss iuishnGonohhetavidd old ood Shien ease aoed ae as eAS 3. 68 9. 35 
MgO 3.95 | 13.75 
CaO. 8. 26 10. 48 
ae 5. a 1.58 
v} es i . 85 
H2O at 110°.... siete c -52 
H20O above 110°....... : 4 i 2.44 \ “0H 
i Sosenias Sarda 3 a es 1. 83 
205. Z 11 
Cg Og oases becca dadeas ie De lSec ca sesadd ay aeuss shee deisel Sie dea iciaadisnle Dc Maas ouaseuraisa Poate ae ne ell bees Pane eae Ihde Zeie ac 410 
ae ie 
Ow: Se eareaccon 
Ba). ciocctcanannes sec 31 trace 
Dig sink ses eonmosew sea mneninsets seetincuet sateen seat trace! | icc secs 
COB orate satpercies cietdapa semanas qsteatnsnianbineinaiame ss oem eeiaase 2A ees ae walle grees 8542) lesacesners 
SO geo: cance carer veer send nedanntwite tannin ce orleans stesso WUD aaetarscccspsraiers cvatsietate O42 Semrecine 
ly sea de kkiexeusareteewar tiv ened mundes yretinwee ss rengedenede ao trace: |isvesersfeaehenes skeet atl ears igh 
| 
| 99.11 | 100.15 | 100.04 | 100.13 
5. LITTLE BELT MOUNTAINS. 
Rocks collected by W. H. Weed and L. V. Pirsson. Described in a paper on the 
Neihart and Barker mining districts in Pt. III of the 20th Ann. Analyses by W. F. 
Hillebrand, record No. 1476, and H. N. Stokes, record No. 1547. 
A. Rhyolite porphyry, Yogo Peak, sheet at head of Belt and Running Wolf creeks. 
Toscanose. Phenocrysts of orthoclase and quartz in a groundmass of quartz and 
alkali feldspar, with a little white mica and some kaolin. Chlorite, limonite, and 
calcite are also present, pseudomorphous after biotite and perhaps hornblende. Total 
amount of secondary minerals very small. Analysis by Hillebrand. P. R. C. 1474. 
B. Granite porphyry, Wolf Butte. Toscanose. Phenocrysts of quartz, orthoclase, 
plagioclase, and biotite in a groundmass of quartz and alkali feldspar. A little apatite 
and iron ore, with secondary calcite, limonite, chlorite, and white mica. Analysis 
by Stokes. P. R. C. 1475. 
C. Granite porphyry, top of Barker Mountain. Toscanose. Phenoerysts of ortho- 
clase, oligoclase, biotite, green hornblende, sphene, and iron ore, in a groundmass of 
quartz and alkali feldspar. Also a little apatite and some secondary chlorite and 
limonite. Analysis by Stokes. P. R, (. 1476, 
