Schaller — Probable Identity of Podolite 'with DahUite. 30!) 



Art. XXXIII. — The Probable Identity of Podolite with 

 DahUite; Lj Waldemak T. Schaller. 



A COMPARISON of the properties and clieniieal composition of 

 podolite and dahllite shows them to be essentially identical. 

 Dahllite was described in 1888 by Bi-ogger and Biickstrom,'''' 

 and a description of it is given in Dana's System of Mineral- 

 ogy, p. 866. Podolite was described by Tschirwinskyf in 

 1907, and the summary of the properties of the two minerals 

 given below has been prepared from the printed descriptions. 



Dahllite 

 Occurs in crusts with fibrous 

 structure, on apatite. 



Density is 3-053. 



Color is pale yellowish white. 



Uniaxial, negative. 



Double refraction and index 

 of refraction slightly greater 

 than that of apatite. 



Soluble in cold dilute acid with 

 evol. of C0„. 



Podolite 



Occurs in crystalline masses or 

 in prismatic crystals on phos- 

 phorite, also in spherulitesof 

 prismatic crystals. 



Density is 3-077. 



Color is j^ellowish. 



Apparently hexagonal, crystals 

 show optical anomalies, nega- 

 tive. 



Double refraction somewhat 

 greater than that of apatite. 



Mean index of refraction 1 ■%^^b. 



Soluble in HCl with evol. of 

 C0„. 



Compo- 

 sition 



H.Ca,,P,C,03,or 

 2Ca3P,0,.CaC03.iH,0 



See below. 



Compo- 

 sition 



Ca,„P,CO,, or 

 3Ca3P,0,.CaC03 

 See below. 



To better compare the two formulae, they are given below 

 with Ca given in constant amount. 



Dahllite. H,„Ca,„P,„C,„0„, 



Podolite Ca„P„C,0,3, 



The analyses of the two minerals are shown in the follow- 

 ing table for comparison : 



* Brogger, W. C. and Backstrom, H. Dahllite, a new mineral from Ode- 

 garden. Bamle, Norway, Meddelanden fran Stockholms Hogskola, No. 77 

 in Ofr. Vet. Akad. Forh'., 1888, p. 493. Abstractedin Zeit. Kryst. Min., vol. 

 xvii, p. 426, 1890. 



t W. Tsohirwinsky. Podolite, a new Mineral, Centr. Min. Geol. Pal., 

 1907, p. 279. For some earlier but incomplete descriptions in Russian pub- 

 lication, see abstract thereof in Zeit. Kryst. Min., vol. xlvi, p. 296. 



