







Defici- 



P0 4 



F 



CI 



H 2 



Misc. ency Total 



57-31 



0-23 



0-12 



0-35 



3-18 0-72 99-97 



55-24 



— 



0-81 



0-44 



3-96 1-48 100-89 



55 53 







1-52 



0-22 



3-10 1-30 99-90 



53-12 



1-03 



1-82 



0-46 



3-80 1-39 99-89 



57-50 



0-62 







0-15 



1-37 100-08 



57-07 



1-20 







0-30 CO 3 =0-23 092 99'55 



Rogers — Dahllite (Podolite) from Tonopah, Nevada. 479 



Oxygen 



Ca 

 Mt. Greiner et Gol- 



ling* 38-06 



Krageroe, Norway -f. 38 "96 

 Krageroe. Norwayf. 38 "73 



Ceylon}.' 38'27 



Zillerthal§ 40 '44 



Zillerthalj 39*83 



The existence of the compound 3Ca 3 (P0 4 ) 2 .CaO is proved by 

 the analyses^ of Voelcker, Hoskyns-Abrahall, Carnot, and 

 Postma. For a mineral with this composition or one in which 

 this molecule predominates I propose the name vcddcerite, as 

 Voelcker was the first investigator to show that apatite was 

 sometimes deficient in fluorine and chlorine. Hoskyns-Abra- 

 hall wrote the formula for apatite thus : Ca 10 (PO 4 ) 6 (O,F 2 ,Cl 2 ). 

 Groth** substitutes hydroxyl for oxygen, principally for a 

 priori reasons. In the above analyses the water percentage 

 is too low to make up the deficiency as hydroxyl, the average 

 being 0*32 as against 1*19 for oxygen. The isomorphism of 

 voelckerite with fluor-apatite and chlor-apatite may also be 

 explained by mass-effect isomorphism, one atom of oxygen 

 replacing two atoms of fluorine. 



Thus we have four isomorphous compounds : 



Fluor-apatite 3Ca 3 (P0 4 ) 2 .CaF 2 



Chlor-apatite 3Ca 3 (P0 4 ) 2 .CaCl 2 



Dahllite 3Ca 3 (P0 4 ) 2 .CaC0 3 



Vcelckerite 3Ca 3 (P0 4 ) 2 .CaO 



The names fluor-apatite and chlor-apatite are well established 

 in the literature. The name carb-apatiteff was proposed for 

 the carbon o-phosphate but was withdrawn in favor of podolite. 

 Dahllite, however, has priority over both carb-apatite and 

 podolite. Voelckerite is a better name than the name oxy- 

 apatite suggested by analogy and gives recognition to Voelcker 

 for his work on the chemical composition of apatite. On 

 account of the difficulty of recognizing these minerals without 

 chemical analysis, apatite may be used as a group name, the 

 general formula being 3Ca 3 (P0 4 ) 2 .Ca(F 2 ,Cl 2 ,C0 3 ,0). 



Besides 3Ca 3 (P0 4 ) 2 .CaC0 3 , a number of other calcium 

 carbono-phosphates have been described. They are as follows : 



* Carnot, Bull. Fr. Soc. Min., xix, 135. 



f Voelcker, Ber. Ch. Ges., xvi, 2460, 1883. 



\ Jannasch, Zs. anorg. Chem., vii, 154, 1894. 



§ Hoskyns-Abrahall, Zs. Kryst. , xxi, 389. || Postma. 



TT In the case of the Norwegian apatites, which contain chlorine but no 

 fluorine, there is no doubt of this, for the chlorine determination is a very 

 accurate one. 



** Tab. Uebersicht der Mineralien, 4th ed., p. 87. 



ft Tsohirwinsky, loc. cit. 



