1892.] Mineralogy and Petrography. 57 



and ch'ibazite are ascribed to the same causes as those assigned to tin- 

 anomalies of analcite. — Some doubt having been cast upon the correct- 

 ness of Baumhauer's conclusion that nepheline btrapezohedrallv heni- 

 hedral, the mineral from three bombs of Vesuvius has again been ex- 

 amined. The figures produced on the oo P faces of crystals, upon etch- 

 ing with HC1 and H F, are ■ imsymmetrical ; consequently their crys- 

 talization is either pyramidal or trapezohedral hemihedral, and the 

 forms are hemimorphic with respect to the vertical axis. 1 — Saltmair 

 records tbe following as the composition of a melanite from Oberroth- 

 well in tbe Kaiserstubl: 



Si0 2 Ti0 2 Zr0 2 A1 2 3 Fe 2 3 Mn 2 3 FeO CaO MgO Na 2 < ) K < ) Lou 

 30.48 11.011.28 3.13 15.21 .28 3.84 30.19 2.28 1.65 .19 

 It is interesting for tbe large percentage of titanium shown by it, and 

 for the considerable quantity of zirconium, which 1ms heretofore never 

 been found in any member of tbe garnet group. — After examining criti- 

 cally more than fifty analyses of vemvianite, Kenngott 3 concludes that 

 the composition of the mineral must be represented by a formula of two 

 parts, like that of apatite. The silicate portion may be represented by 

 4 (2 RO. Si0 2 ) + 2 EA, 3 Si0 2 [=4 R", SiO, + R'" 4 (SiO,),]. The 

 composition of the non silicated portion is not yet known, but it prob- 

 ably contains the hydroxide group, sodium, potassium, and sometimes 

 fluorine, in varying proportions. — .4 Imogen' crystals from the Picde- 

 Teyde, Teneriff are tabular in habit. They are negative and crys- 

 talize monoclinically with a : e=l : .825. /5=97°34'.— Rose colored 

 dodecahedral garnets from Xalostic, Mex., have been analyzed by De 

 Landero. 5 Their density is 3.516 and hardness 7.5. Their composi- 

 tion corresponding to (Ca Mg) ;i Al Fe) 2 (SiO,):,, is: 



Si0 2 A1 2 3 FeA CaO MgO MnOBaO Res. 



40.64 21.48 1.57 35.38 .75 tr. .17 



—Some good sections of pericline from the Pfitschthal, Tyrole, have 

 been very carefully studied by Miinzig." Their optical properties in- 

 dicate that the substance is not a pure albite, but that it is an inter- 

 growth of oligoclase (ab-an) with albite. The former comprehends the 

 larger part of the pericline crystals, tbe latter appearing in it as imall 

 irregular flecks. Both feldspars are twinned according to the pericline 

 law, with the albite apparently occupying pores in the oligoclase.— Des 

 ^aumhauer : Zeits. f. Kryst. XVIII, p. 611. 

 2 Ib. p. 628. 

 3 Neues. Jahrb. f. Min., etc., 1891 , I, p. 200. 



