56 G. H. Williams — Piedmontite and Scheelite, etc. 



attempt was made to isolate it. There is no reason to believe 

 that it is not the same mineral as that concentrated in the veins. 



As piedmontite is con- 

 stantly increasing in impor- 

 tance as a rock constituent, 

 it has appeared to the writer 

 worth while to record all 

 occurrences heretofore pub- 

 lished. As far as possible 

 he has made a comparative 

 study of these occurrences.* 

 We notice in epidote a 

 tendency to form red varie- 

 ties, just as, in the case of 

 hornblende, there is a ten- 

 dency to form blue ones 

 (glaucophane, riebeckite, gas- 

 Fig. 2. taldite, crocidolite). Thulite 



Occurrence of microscopic p ; edmontite in is red zoisite. The red epi- 

 minute veins with secondary quartz and dote f R ot herkopf in the 

 surrounded by rims of epidote. Magnified ^ , , , L . ./; ., „ 



x 25. JLyrolf and the withamite of 



Glencoe in Scotland contain 

 very little manganese, and are comparable with the rose epi- 

 dotes associated with the microscopic piedmontite of South 

 Mountain and Japan. £ The recorded piedmontite occurrences 

 which the writer has been able to find are as follows :§ 



1. With manganese ore deposits. — San Marcel,* Viu, and 

 Mezzenile, Italy! (piedmontite); Jakobsberg,* Sweden^ (man- 

 gan-epidote, with MnO only). 



2. Spkerulitic aggregates as veins in eruptive rocks. — 

 Grlencoe,* Scotland** (withamite) ; South Mountain,* Penn. 



3. Secondary constituent of eruptive rocks. — " Porfido rosso 

 antico," Djebel Dokhan,* Egyptff ; Quartz porphyries of Mis- 

 souri ;* XX granulite of Haute-Loire, France ;§§ South Moun- 

 tain,* Penn. 



* For assistance in gathering material for this study the writer would express 

 his gratitude to Mr. C. IS. Bement of Philadelphia ; Mr. J. S. Diller of Washing- 

 ton; Prof. L. V. Pirsson of New Haven; Prof. B. Koto of Tokyo; Prof. G. 

 Flink of Stockholm and Prof. A. Lacroix of Paris. 



f H. Bucking: Zeitschr. f. Kryst., vol. ii, p. 384, 1878. 



%B. Koto: Jour. Coll. Sci., Imp. Univ. Japan, vol. i, p. 310, 1887. 



§ Asterisk denotes specimens studied by this writer. 



|| Laspeyres : Zeitschr. f. Kryst., vol. iv, p. 435, 1880; Jervis, quoted by 

 Hintze: Handb. Min., p. 255, 1890. 



1 G. Flink: Zeitschr. f. Kryst., vol. xv, p. 88, 1889. 



**D. Brewster: New Edinb. Journ. Sci., vol. ii, p. 218, 1825: Heddle : Min. 

 Mag., vol. v, p. 15, 1882; Lacroix: Bull. Soc Min. de Fr., vol. vi, p. 75, 1886. 



ff H. Rosenbusch: Die mass. Gest.. 1st ed., p. 290, 1877 ; 2ded., p. 472, 1887 ; 

 Th. Liebisch: Zeitschr. d. geol. Ges., vol. xxix, p. 717, 1877. 



±X B. Haworth: Inaug. Dissertation, Am. Geologist, vol. i, p. 365, 1888. 



§§ Lacroix: Mineralogie de la France, vol. i, p. 155, 1893. 



