G. H. Williams — Crystals of Pyroxene. 275 



Art. XXXI. — Note on some remarkable Crystals of Pyroxene 

 from Orange County, N. Y. ; by George H. Williams. 



Certain yellowish gray crystals of pyroxene occurring in 

 the crystalline limestone of Orange County, N. Y., have a very 

 peculiar tabular habit produced by the unusual development 

 of the basal pinacoid. Dr. Lewis Beck figures these crystals in 

 his Mineralogy of New York,* although his drawing wrongly 

 represents the basal plane in the position of the orthopinacoid, 

 for which he evidently mistook it. Beck gives the locality for 

 these crystals as two and a half miles north of Edenville. In 

 1860, Professor Gr. vom Bath described and figured some of the 

 same crystals from the collection of Dr. Krantz in Bonn.f He 

 gives the locality where they are found as "Warwick, Orange 

 Count}^ N. Y., which is probably less accurate than that given 

 by Beck. Vom Rath's first figure represents a crystal of the 

 ordinary habit; tabular according to the base (c) and showing 

 besides the forms : coPoo (a), oo P oo (&), oo P (ra), P (s), 2P (o) 

 and — P (w). His second figure represents a twin crystal of a 

 more prismatic habit, formed according to the common law for 

 pyroxene. This shows, in addition to the above named planes, 

 the form Poo(p). Vom Rath further mentions the striation of 

 these crystals parallel to their basal pinacoid, which he refers 

 to an irregularity of growth, although he was the first subse- 

 quently to explain it as due to twinning.:}: He also says that 

 they are externally changed by paramorphism to an aggregate 

 of fine hornblende needles, which produces a lustrous shimmer 

 on the surfaces. 



Professor Des Cloizeaux also mentions and figures these crys- 

 tals in the first volume of his " Mineralogy " published in 1862. § 

 His first figure is like vom Rath's and represents a similar sim- 

 ple crystal. His second shows a hemimorphic development in 

 the direction of vertical axis, there being on one side of the 

 prismatic zone the forms: OP (p), P (s), 2P*(o), Poo (e), and 

 -2P2 (ji) ; and on the other side: OP (p), -P (u) and -|P3(a) 

 No mention of twin crystals from this locality (given as War- 

 wick) is made by Des Cloizeaux. 



A remarkably fine group of these Orange County pyroxene 

 crystals, which came into the possession of the Johns Hopkins 

 University mineral cabinet with the purchase of the collection 

 of the late E. W. Root of Clinton, N. Y., seems worthy of a 

 brief notice on account of the singularity of their form. This 



* Mineralogy of Sew York. Albany, 1842. 4°, p. 293, fig. 215. 



\ Pogg. Ann., Bd. cxi, p. 263, taf. iii, figs. 5 and 6. 



% Zeitschrift fur Krystallographie, v, p. 495, 1881. 



§ Manuel de Mineralogie, vol. i, p. 54, 1862. Atlas, figs. 57 and 58. 



