DALY. — VARIETY OF HORNBLENDE. 437 



of fourteen chemical and optical analyses of enstatite wherein the optical 

 angle in oil continuously decreases from 133^ 8' (red light) to 59^ 20' 

 (green light) while the percentage of (FeO plus MnO) simultaneously 

 increases from 2.76% to 33.6%. 



This hornblende is thus unique among the species yet described in that 

 it possesses the combination of properties including an unusually small 

 optical angle, an unusual pleochroism and absorption scheme, a well de- 

 veloped zonal structure, and quite anomalous etch-figures with hydro- 

 fluoric acid on the prism (110) and on the clinopinacoid. 



For convenience of reference, this variety of amphibole may be called 

 philipstadite, from the name of the locality whence it was derived. 



