wherry: phosphate and silicate minerals 



107 



described by Zimanyi 4 as a dense (dicht, derb) white, meerschaum- 

 like substance with the (rather improbable) ratios A1 2 3 : P2O5 : H 2 

 = 4:3: 30, associated with a similar material with the ratios 3:2:17. 

 It seems likely that these are really the same mineral, the ap- 

 parent difference, in ratios being due to the impure character 

 of the samples analyzed. In Doelter's Handbuch der Mineral- 

 chemie this mineral is listed as amorphous, 5 but a specimen 

 labeled vashegyite in the collection of Colonel Roebling has been 

 found by Dr. E. S. Larsen, Jr., to be cryptocrystalline with an 

 index of refraction of 1.480 and double refraction 0.002. 6 A com- 

 parison of the properties of the present mineral and vashegjdte 

 is given below: 



Manhattan mineral Vashegyite 



Color pale green white to yellowish 



Luster vitreous dull 



Hardness 3.5 2.5 



Specific gravity 1.9S 1.964 



Structure amorphous, glass-like compact, meerschaum- 



like 

 Optical character isotropic anisotropic, cryptocrys- 



talline 



Index of refraction variable, 1.48 to 1.50 1.480 



Double refraction absent very weak, about 0.002 



Ratio A1,0 3 : P 2 6 : H 2 0... . about 3: 2: 18 3: 2: 17 or 4: 3:30 



Impurities considerable, including very small in amount 



copper oxide, yield- 

 ing the green color 



Occurrence associated with variscite "In the immediate 



neighborhood of var- 

 iscite" 



The differences in optical properties can be explained as due 

 to the vashegyite examined by Dr. Larsen being a "metacolloid," 

 a colloid exhibiting incipient crystallization, while the Man- 

 hattan mineral is still essentially amorphous; the difference in 

 color is attributable to the presence of copper in the latter. 7 

 The two minerals thus agree to a sufficient extent for them to 

 be regarded as identical. 



4 Math. term. Ert. 27: 64. 1909; Zeits. Kryst. Min. 47: 53. 1909. 



5 Handbuch der Mineralchemie, 3: 465. 1914. , 



6 Private communication. 



7 The copper probably replaces either some of the (AlOH)* groups or H therein. 



