1894.] Mineralogy and Petrography. 421 
have been changed into hornstones and knotty schists. Besides the 
granites the only other intrusives cutting the slates are two dykes of 
minette, both of which show the effects of pressure. One of the dykes 
consists essentially of orthoclase and two generations of biotite. It 
contains also apatite and zircon and large quantities of plagioclase and 
calcite. In the squeezed phase of the rock the biotite has been changed 
to chlorite. The material of the second dyke differs from that of the 
first one, only in that it has been more thoroughly squeezed and con- 
sequently has suffered greater alteration. 
Petrographical News.—Sears’ finds that the porphyritic feldspar 
in the rock from Marblehead Neck, Mass., called by Wadsworth? 
trachyte, are anorthoclases, and that much of the feldspar of its 
groundmass is of the same nature, consequently the rock is a kerato- 
phyre. Analyses of the rock and of one of its phenocrysts follow : 
SiO, TiO, Al,O, Fe,O, FeO MnO CaO MgO K,O Na,O P,O, H,O 
Rock 70.23 .03(?) 15.00 1.99 . 24 33 38 499 4.98 .06 2.19 
Felds. 65.66 20.05 tr. tr. 13 67 .18 6.98 6.56 41 
The report of the State Geological Board of Michigan’ contains 
brief microscopie descriptions of certain eruptive, sedimentary and 
schistose rocks of the Upper Peninsula by Drs. Patton and Lane. 
Among the former are described granites, syenites; serpentine and lam- 
prophyres. Among the sedimentaries graywackes, quartzites and slates, 
and, among the foliated rocks, amphibolites and hornblende schists. 
e amphibolites are principally altered diabases. Quartz diabases are 
mentioned by Lane as existing in dykes cutting graywackes and slates 
that are sometimes changed on the contact into spilosites, and quartz- 
ites that are altered near the intrusive into Lydian stone. Dr. Wads- 
Worth, in the same volume, gives an outline scheme of his classification 
of rocks (eruptive and sedimentary), the principles of which were first 
ennunciated at length in his Lithological Studies.” 
Graeff" has found, in an old hand specimen of tephrite from Hor- 
berig in the Kaiserstuhl, a holocrystalline basic concretion with a 
Structure approaching that of theralite. 
‘Bull. Mus. Comp. Zool., Vol. XVI, p. 167. 
, Proc. Bost. Soc. Nat. Hist., XXI, p. 288. 
„Eep. State Board of Geol. Survey for 1891-92. Lansing, 1893. 
„Mem. Mus. Comp. Zool., 1884, XI. 
Versamm. Oberrh. Geol. Ver. Ber, XXVI, 1993. 
