42 



Rogers — Mineralogical Notes. 



Art. IV. — Mineralogical Notes, No. 2 ; by Austin F. 

 Rogers, Fellow in Mineralogy, Columbia University. . 



1. Calcite* 



(a) Neio Types from the Upper Mississi/pjn Lead Region. — 

 The calcite crystals occurring in the ore district of southern 

 Wisconsin have been studied by Hobbs,f who distinguishes six 

 types of crystals with 13 forms. In the Egleston Mineralogi- 

 cal Museum of Columbia University are three types not men- 

 tioned by Hobbs, including three forms not given by him. 



The most interesting type is represented by two singly ter- 

 minated crystals about 20x30 mm with a fewer smaller ones, 

 and are labelled " Shullsburg, Wis." The dominant form is 

 the pyramid of the second order 7 (8'8*16'3), a rare form for 

 calcite first observed by vom RathJ on Andreasberg crystals, 

 and later by Cesaro§ as a dominant form on crystals from 



Rhisnes, Belgium. HambergJ also found it on crystals from 

 Yisby, Gotland, Sweden ; and recently Penfield and Ford^f 

 described some siliceous calcites from Bad Lands, South 

 Dakota, on which this pyramid is the dominant form. Pen- 

 field and Ford** have also described crystals from Union 

 Springs, Cayuga Co., !N". Y., on which this form is prominent. 

 The only other forms occurring on_ the Shullsburg crystals 

 are the negative rhombohedron 6(0112), faces of which are 



* Letters given by Dana in 6th Fldition System are used for such forms as are 

 mentioned therein. Goldschmidt's letters are used for the other forms. The 

 letters for new forms are chosen in accordance with G-oldschmidt's table on p. 

 141 of vol. i of his " Index der Krystallformen der Mineralien." 



f Hobbs, Zeitschr. f. Kryst., xxv, 258-261, 1895: also Bull. tJniv. Wis, Sci. 

 Series, i, 114-121, 1895. 



% vom Rath, Pogg. Ann., cxxxii. 521, 1867. 



\ Cesaro, Mem. l'Acad. Roy. de Belgique, xxxviii, 8-14, 1886. 



I Hamberg, Geol. Foren. Forhandl., xvi, 709-716, 1894. 



"U Penfield and Ford, this Journal, ix, 352-354, 1900. 



** Penfield and Ford, this Journal, x, 237, 1900. 



