2l8 



NEW YORK STATE MUSEUM 



Many of the specimens formerly obtained showed large and beau- 

 tiful calcite combinations. Those which through Mr Hawkins's 

 kindness are available consist of built-up individuals formed of 

 two superposed types in parallel position and evidently represent- 

 ing two generations of calcite deposition. The compound indi- 

 viduals average 30 millimeters in vertical length. The crystal 

 elements of these compound groupings which represent the earlieY 

 generation are rhombohedral in habit. In some instances this habit 

 occurred sufficiently free from the superimposing secondary habit 

 to admit of the determination of the modifying forms. The sim- 

 ple individual of this generation is shown in figure 1 and consists 

 of the negative rhombohedrons <5. (01 12) and 77. (0881) modified 

 by the forms a (1120), 1x1.(4041), K:(2i3i), 1(8.5. 13. 3) and 

 s :( 17.13. 30.4), the latter of which is new to the species. The 

 crystals of this generation which are slightly more purplish in 

 color and more transparent than those of the superposed second 

 generation in several instances appear as phantoms within the 

 latter. The superposed crystals of the second generation, which 

 are transparent to translucent and slightly yellowish in color, are 

 scalenohedral in habit. They are superimposed in parallel position 

 upon the lateral solid angles of the rhombohedral habit of the 

 51(17.13.30.4), the latter of which is new to the species. The 

 first generation in the manner shown in figures 2a and b. The 



dominant form is a new negative scalenohedron - - R - = 



(3. 13. 16.8)) to which the letter t has been assigned. The scaleno- 

 hedral habit is terminated by the negative rhombohedron v. (0554) 



= _ 1 R the two forms lying in the zone [0554.1 120]. In ad- 

 4 



dition to the foregoing the new scalenohedron lies in zone with 

 the planes 1102 = 8, and 0881 = II. both of which are present in 

 considerable development on the rhombohedral crystals of the first 

 generation. In general habit the superimposed crystals conform 

 closely to that shown in figure 552B of Dana's System of Min- 

 eralogy, fifth edition, from Bergen Hill. The calculated angles 



7 3 — 

 for the negative scalenohedron - - R -= (7.35.42.20) assigned 



5 2 



to this combination are X = 87° 14', Y=I5° 52' and Z = 



68° 14'. The measured values of the angles Y and Z for the nega- 



- g 



tive scalenohedron t — — - R- = (3. 13. 16.8) are: 



Y = 17 46'; 17 18'; 17 48' and 17 11'. 

 Z = 6g° 11'; 69 20'; 68° 51' and 69 3'. 



