﻿W. E. Hidden — Contributions to Mineralogy. 207 



parent crystal having a prism of 4 mm square, was 17 mm long 

 and had the zirconoid 3-3 and 3 largely developed. An 

 analysis by Mr. J. B. Mackintosh showed the presence of 34*05 

 per cent of phosphoric acid combined with a base considered to 

 be yttria but not tested. 



In the auriferous gravels of middle western North Carolina, 

 northwestern Georgia and eastern Alabama, the writer has fre- 

 quently found xenotime along with monazite, etc. Some of 

 the localities are in Hall Co., Gra., Burke, Polk and McDowell 

 Counties, N. C. I have been most successful in the drift from 

 the Pilot Mt. in the lower edge of Burke Co., N. C, where I 

 found some of the xenotimes symmetrically compounded with 

 zircon (vol. xxi, p„ 244, 1881). 



Twin" Ckystals of Monazite. — In the preceding note on 

 xenotime the occurrence of these beautiful monazite crystals is 

 briefly mentioned. With the single exception of the crystals 

 from this region which formed the 

 basis of Dr. Edward S. Dana's paper,* 

 probably no finer examples of this rare 

 mineral have ever been found. For 

 the most part the crystals are transpar- 

 ent, of a beautiful essonite-red color 

 and are highly polished. They vary 

 in size from four to twenty millimeters 

 in length and thickness. They were 

 prismatic from an unusual extension of 

 + 1 and -\-\-i. The occurring planes, 

 as shown in the figures, are : 



o=«-i (100), w=— l-i(lOl), c=_O(001), g= + l_-*(l01), d=J-i (012), e=U(011) 

 /=2-£(021), b=i-i(0l0),v = + 1(111), 2= + 3-3 (311), $=+2-2 (211), u=-\ (111) 



In addition there were i-% —2-2, I and several other planes 

 which were only slightly developed, and an undetermined 

 orthodiagonal pyramid. Of the above, i\ a, g, z and e were the 

 most frequent and predominating planes, while the prism /was 

 only rarely shown. The twinning plane is a (i-i, 100), the 

 orthopinacoid, which law of twinning was first noticed by vom 

 Kath on crystals from Switzerland. Cruciform crystals were 

 found of almost ideal symmetry, while a few of the crystals 

 were twinned only on one side. 



A distinct but imperfect cleavage parallel to i-i (010), the 

 clinopinacoid, was observed on several crystals, while the com- 

 mon basal cleavage was entirely absent. Efforts to produce it 

 artificially were entirely unsuccessful. 



It is to be noted that turnerite is described as having a perfect 

 cleavage parallel to it, and one less distinct parallel to the basal 



* This Journal, vol. xxiv, pp. 247-250. 



