1889.] Mineralogy and Pctrogi-aphy . 1007 
the augite only into the altered olivine, along what were probably the 
cleavage cracks of the fresh mineral. A specimen of the variety of 
picrite known as scyelite was discovered by Bonney^° in the island 
of Sark, British Channel. It consists of serpentinized olivine, altered 
augite, bleached mica, some of which exhibits a banded twinned struc- 
ture, one set of bands extinguishing parallel to the cleavage of the 
mineral, and the second 18° from this. The rock was not found in 
place.— r — The separation of large quantities of apatite from the 
gneiss of Freiberg and the granite of the Kinzigthal has given Steltz- 
ner" the opportunity of comparing their composition. He found that 
the apatite from the gneiss corresponds to the formula loCag (POJ^-f 
sCaFj, while that from the granite accords better with the formula 
i3Ca3 (Po,),+4CaF,. 
Mineralogical News. — A number of yellow grains of monazite 
[(Ce, La, Di) PO J having been found in the sands from various locali- 
ties in Brazil, more particularly in the neighborhood of Rio Janeiro 
and in the diamond fields, Mr. Derby^^ ^^s sought for the mother rock 
containing the mineral, and has found it in the biotite-gneiss, granites 
and syenites of the region. His method of operation was to grind 
into powder a large quantity of the decomposed rock and wash it in 
the manner made use of in the search for alluvial gold. A full descrip- 
tion of the mineral and the rocks in which it occurred is promised in 
due time. Measurements of fifteen crystals of polybasite from five 
different localities afford Miers^^ data for the determination of the axial, 
ratio of this mineral with some degree of accuracy. He finds it to be 
<3!.-/5 .•<:= 1,7262 : I : .6344. Crystals with an apparently hexagonal 
habit are in reality twins, with the twinning plane o=P. The exami- 
nation of eighteen crystals of aikinite from Beresovsk, Urals, affirms the 
conclusion that the mineral is orthorhombic. The prismatic angle is 
82° 22. Among a few minerals from the Ardennes and Belgium 
analysed by Klement^^ attention may be called to a chromiferous 
mica, occurring in small flakes on vein quartz from Salin-Chateau, 
Belgium. The lamellae are non-elastic, but their composition ap- 
proaches that of muscovite, viz.: 
Si,0 Al,03 Cr./:>3 Fe.p, CaO MgO K^O Na^ Li,0 H,0 
45.68 34.17 .84 2.35 .27 3.84 4-47 2.23 tr 4.65 
" Geol. Mag., Mar., 1889. p. 109. 
