144 Field Columbian Museum — Geology, Vol. III. 



terize the Joplin calcites, as described by one of the authors.* 

 The average development of the forms is shown in the accom- 

 panying figure, Fig. 2. The planes of the different forms show 

 readily recognizable peculiarities. Thus the planes of v (2131) 

 usually have brilliant, more or less undulating surfaces, those of r 

 (10I1) are roughened like ground glass, and those of w (31I5) are 

 smooth. The substance of the crystals is semi-transparent and 

 amethystine in color. Needles and flakes of marcasite are included 

 in large numbers through the substance. Fragments of the calcite 

 phosphoresce with a warm yellow light when moderately heated, 

 although Headdenf found only the yellow Joplin calcite phosphor- 

 escent. The largest crystals measure a foot in length and weigh 

 20-30 lbs. 



CALCITE 

 BELLEVUE, OHIO 



FIG. 1, PLATE XLIX 



A crystal of calcite (Mus. No. M 10372) kindly presented to the 

 Museum by Mr. S. A. Kurtz, Principal of the Bellevue High School, 

 shows some unusual features. The crystal is of the " dog-tooth " form 

 and would appear on casual glance to be a polar half of a scalenohed- 

 ron. It is 2.5 cm. in length and composed of colorless, transparent 

 calcite. Mr. Kurtz states that such crystals occur at a depth of about 

 twenty feet from the surface in a hard, blue layer of the Niagara lime- 

 stone at Bellevue. An examination of the crystal with the reflecting 

 goniometer shows that its fundamental forms are not scalenohedrons 

 but pyramids of the second order. . The dominant one of these is y 

 (8. 8.16. 3). This, it is of interest to note, was found by Penfield and 

 Ford to be a dominant form on silicious calcite from the Bad 

 Lands, Nebraska, J and Union Springs, New York.§ Rogers also 

 found it a dominant form on calcite from Shullsburg, Wisconsin. || 

 The next pyramid of the Bellevue specimen cuts the vertical axis at 

 one half the height of y, its symbol being « (4483). Above this occurs 

 the pyramid it (1123) cutting the vertical axis at one fourth the height 

 of «. The pyramids are thus in Dana's symbols, V" 2 > I" 2 anc ^ f~ 2 - 



* Farrington, Pub. Field Col. Mus., 1900, Geol. Ser. Vol. I, pp. 232-241. 



t Am. Jour. Sci., 1906, 4, 21, p. 301. 



% Am. Jour. Sci., 1900, 4, 9, p. 353. 



§ Am. Jour. Sci., 1900, 4, 10, p. 237. The Union Springs occurrence was further studied by 

 Whitlock (Bull. 98, New York State Museum) and the conclusion reached that the pyramidal 

 habit was produced by crystallization from a highly siliceous solution. 



11 Am. Jour. Sci., 190*. 4, 12. P- 42. 



