.256 MiNERALoar. 



like structure. It is found in " pockets,'' sometimes over 100 feet 

 wide, associated with mammalian remains resembling those of the 

 gypseous deposits of the Paris Basin. W. T. 



Rumpf, J. Feldspathfiihrender Kalkstein vom Sauerbrunngrahen 

 bei Stainz. [Limestone with Eelspar.] Mm. Mitt. Heft iii. p. 207. 



A felspar rich in soda occurs with muscovite, quartz, tourmaline, 

 garnet, &c. in a granular limestone from the Sauerbrunngraben, near 

 Stainz. F. AV. R. 



Rutley, F. Notes on some Peculiarities in the Microscopic Structure 

 of Felspar. Qttart. Journ. Geol. Soc. vol. xxxi. pp. 479-488, 

 pis. xxiii., xxiv. 



The obseiTations recorded relate mainly to some exceptional features 

 in the striation of felspars, involving a consideration of the extent to 

 which dependence may be placed on the discrimination of monoclinic 

 and triclinic felspars by the methods usually recognized in microscopic 

 research. Some other peculiar structural features are noticed ; and the 

 effects which might be produced on polarized light by the overlap of 

 twin lamellae in thin sections of felspars, when cut obliquely to the 

 planes of twinning, are considered. The conclusions mostly relate to 

 matters of detail ; but the general inference is that the present method 

 of discriminating between monoclinic and triclinic felspars by micro- 

 scopic examination answers well enough for general purposes, although 

 it is often inadequate for the determination of doubtful examples, 

 which are more frequent than one suspects. F. E. 



Sadebeck, Dr. A. Studien aus dem mineralogischen Museum der 



Universitiit Kiel. [Studies from the Mineralogical Museum of 



Kiel University.] Pogg. Ann. Bd. clvi. pp. 554-563. 



1, a new law of twinning in the regular sj'stera, observed in native 



iron ; 2, twin-striae on titanic iron and iron-glance ; 3, twins of white 



lead-ore according to the law — twin-axis the normal to a face of the 



vertical prism (« : 3 6 : go c) ; 4, a peculiarly- developed crystal of oligo- 



clase from Bodenmais in Bavaria ; 5, goniometric improvements. 



F. W. R. 



[Crystallography.] W. Jahrh. Heft i. pp. 43, 44 ; woodcut. 



Refers to the extension of the author's researches on Kry stall oteh- 

 tonik, mentioned in his essay on Galena. [See Geological Record for 

 1874, p. 247.] By studying subindividuals on faces of crystals he 

 concludes, e.g., that a cube in galena is to be regarded as the limiting 

 form of the icositetrahedron, whilst a cube in fluor-spar is the limiting 

 form of the tetrakishexahedron. F. W. R. 



Sandberger, F. Ueber merkwiirdige Quecksilbererze aus Mexico. 



[Remarkable Mercury-ores from Mexico.] ^^ttz. math.-phys. CI. 



l\ h. Ak. Wiss. pt. ii. p. 203. 



The mineral containing antimony and mercury from Sinaloa in 



Mexico has been found to be a pseudomorph after antimony glance in 



