RECORDS. 653 



with sudden projections of portions of the faces. Striations 

 sometimes occur on the faces of some ciystals, not like those of 

 a plagioclase, but rather hke insets of the feldspar along cleavage- 

 lines of the calcite-filling of the geode. The curvatures, slight 

 distortions and striations look like effects of intense pressure at 

 the contact-surfaces of feldspar and calcite. 



Physical Characters. — Lustre almost vitreous. Color, deep 

 orange to brick-red. Hardness about 6. 



Specific gravity, 2.455, i^"* distilled water at 21° C. This is 

 extraordinarily low for the mineral, to which only one previous 

 determination corresponds, that of a reddish orthoclase from 

 Marienberg, Saxony, the gangue of tinstone, for which Kroner 

 found the specific gravity to be 2.44. 



The mineral is opaque, and, in thin section under the microscope, 

 this is found to be due to the general diffusion of cloudy matter, 

 either white (kaolinic) or bright orange (iron-oxide), with scat- 

 tered black opaque granules. Translucent spots occur only at 

 rare intervals, and all the indications point to incipient alteration, 

 with little or no removal of material. 



Many minute irregular clefts and fissures also traverse the 

 mineral, occupied by films of iron-oxide, and seem to indicate a 

 slight disintegration or shattering of the material, perhaps by ex- 

 pansion ; this also may have a bearing on the origin of the curva- 

 ture above described. 



Clicinical Composition. — The material for the analysis was care- 

 fully picked out to eliminate granules with adhering calcite, in 

 preference to treatment with dilute acid. The latent porosity of 

 the mineral and partial solubility of its amorphous coloring ma- 

 terial were shown by the bleaching produced on the edges of 

 fragments, after digestion in acids. The material was dried at 

 100° C. 



The cobalt-oxide was verified by test of residue before the 

 blowpipe. This and the manganese-oxide may have been both 

 derived in part from a chlorite-mineral whose decomposition has 

 produced both the talc-like scales and black stains (pyrolusite) 

 within the geodes. The water, expelled only on ignition, may 

 have been retained in combination with decomposition-products, 

 and a part of the lime with undetermined carbonic acid. 



