42 INFRA-RED TRANSMISSION SPECTRA. 



TURQUOISE (AlPCuAKOH^+H-O). 

 (Massive, light green; subtranslucent in section of o.i mm. Curve a, fig. 27.) 



This mineral is supposed to contain a molecule of water, although 

 Miers writes the formula without it. The OH groups will cause a 

 band at 3 /u,, and in general the substance is opaque so that it is difficult 

 to decide that question. 



The region at 3 p. is complex, with the maximum at 3.3 p.. There are 

 other bands at 5.1, 5.3, 5.6, 6.3, and 7.6 p, all of which are small. There 

 seem to be no bands belonging to PO 4 . 



LAZULITE, (MgFe)AU(OH)i(PO) 2 . 



(Massive; blue by transmission; ^ = 0.19 mm. Curve b, fig. 27.) 

 The 3 ju, band is prominent, while a new band appears at 4.3 /*. 



/ 2 * s G 7 



FIG. 28. Hydrargillite (a); Diaspore (*) ; Datolite (c). 



9JU 



HYDRARGILLITE (A1(OH) 3 ). 

 (Stalactitic mass; t = o.2 mm.; subtranslucent. Curve a, fig. 28.) 



The section obtainable was only about 6 mm. long, which did not 

 cover the entire slit; hence the capacity is not quite so great as it 

 appears. 



There is only one large band, at 3 /x, which is no doubt due to the 

 OH radicals. 



DIASPORA A1O( OH). 

 (Cleavage piece parallel to b; t = o.iS. Curve b, fig. 28.) 



The specimen was transparent, with a few patches that were trans- 

 lucent. The specimen came from Professor Penfield. The band at 3 /A 

 is wider and not so well defined as in the preceding. There are smaller 

 absorption bands at 1.9, 5.8. and 6.7 /*. 



