Vol. 6] 



EaMe : Neocolemanite. 



185 



Neocolemanite 



Gdt. 



Miller 







oo 

 co 



02 

 01 

 —30 

 —20 

 24 

 23 



6 



-21 



001 

 010 

 100 

 110 

 210 

 230 

 021 

 011 

 301 

 201 

 241 

 231 

 221 

 661 

 221 

 223 

 263 

 211 



Measured 



90 

 

 89 

 54 

 70 

 42 

 19 

 35 

 9"0 

 90 

 41 

 49 

 60 

 51 

 45 

 16 

 5 

 | 63 



°00' 

 00 

 58 

 09 

 08 

 41 

 58 

 53 

 00 

 00 

 10 

 20 

 12 

 32 

 52 

 47 

 24 

 59 



21°40' 

 90 00 

 90 00 

 90 00 

 90 00 

 90 00 

 49 22 

 34 07 

 62 00 

 48 15 

 71 (19 

 68 25 

 65 43 

 79 39 

 57 31 

 20 50 

 47 47 

 51 21 



Calculated 



<t> 



90°00' 

 00 

 90 00 

 54 10 

 70 08 

 42 43 

 19 53 

 35 53 

 90 00 

 90 00 

 41 08 

 49 20 

 60 12 

 57 39 

 45 40 

 16 42 

 5 42 

 63 57 



21°40' 

 90 00 

 90 00 

 90 00 

 90 00 

 90 00 

 49 26 

 34 08 

 62 02 

 48 20 

 71 04 

 68 25 

 65 40 

 79 21 

 57 32 

 20 55 

 47 53 

 51 22 



Colemanite 



Eakle 



90°00' 

 00 

 90 00 

 53 53 

 69 58 



18 38 

 34 00 

 90 00 

 DTi 00 



45 56 



20°07' 

 90 00 

 90 00 

 90 00 

 90 00 



48 54 

 33 13 

 61 49 

 48 18 



57 22 



64 11 51 16 64 12 51 12 



Goldsohraidt 



90°00' 

 00 

 90 00 

 53 57 

 70 00 



18 57 

 34 13 

 90 00 

 90 00 



45 58 



20°13' 

 90 00 

 90 00 

 90 00 

 90 00 



48 50 

 33 13 

 61 47 

 48 14 



57 18 



The pole of the crystals is almost midway between the normals 

 to the base and rear dome (T01), consequently the angles for 

 positve terminal faces are quite similar to those for negative 

 faces. If the neocolemanite is reversed in position so that all of 

 the positive forms become negative and vice versa, then the read- 

 ings would correspond closer to those for forms on colemanite, 

 and only the forms (230), (661), (223) and (263) would be new, 

 they becoming respectively (230), (561), (123), and (163). 

 There would also be more correspondence in the optical orienta- 

 tion. However, the two minerals have a similar basal cleavage 

 and it was by this cleavage that the crystals were oriented. 



Determination of the -polar elements. — The method of deter- 

 mining the values of e', fi, /?, p'„, q'„, e, p„, and q„ is fully ex- 

 plained in the author's paper on colemanite, so will not be 

 repeated here. The average of nine direct measurements on 

 the base gave p = 21°41'; e' = tgp = .3973. Since e' = cotg/x 

 then ^ = 68° 20' and f3 = 180 — /i = 111° 40'. An average of 

 twenty-eight readings on the clinodomes gave e' = .3973, thus 

 agreeing with the direct measurements. 



