Brush and Dana — Mineral Locality at Branchville. 211 



The formula is 5RO . 2P t O, . 5H,0 «»r II ,R : .(P< ) 4 ) 4 + 4II,0. 

 The percentage composition calculated for manganese only is: 

 P t O, 38-96, MnO 48*69, B t O L2-35=100. 



Reddingite. 



The species reddmgite has been known thus far only in a 

 few specimen.-, showing it in a granular form of a reddish 

 color, or rarely in octahedral crystals often superficially black 



from oxidation. The material first found though scanty was 

 sufficient to admit of the determination of the form, which was 

 >wn to be similar to that of scorodite and strengite. Among 

 the specimens recently discovered, reddmgite is not uncom- 

 mon, and we have been gratified to obtain it not only well 

 crystallized but also in massive form, perfectly fresh and 

 unaltered. The color is a pale rose-pink, often hardly more 

 than a pinkish-white. The most intimately associated min- 

 erals are fairtieldite and dickinsonite, the latter of which is 

 often imbedded in it in isolated scales or more often in stellate 

 groups of green folia. The octahedral habit of the crystals, 

 which appear in occasional cavities, is usually apparent at a 

 glance, but not infrequently the crystals are distorted by the 

 elongation of a pair of pyramidal planes which gives them a 

 misleading oblique prismatic appearance. The common form 



of the crystals is shown in fig. 3 from our former paper. Some 

 of the crystals are more complex (fig. 4) and show also the unit 

 pyramids ?•, s and t, whose symbols are respectively 338, 223, 

 774. These planes do not give sharp measurements but the 

 angles are sufficient for identification. The axes taken are 

 those previously obtained by us, viz : 



a:h: c = 0-8678 : 1 : 0'9485 



and the measured and calculated angles are, 



Measured, 



Calculated 



111 ^ 338 = 20° 11' 



20° !»' 



111 a 223 = 10° 10' 



9° :. i' 



111 



771 = 15° 41' 



15° 46' 



It seemed especially desirable to have a new analysis of this 

 species, both because the material was more abundant and 



