838 S. L. Penfield — Crystallization of Hcrderite. 



ferent varieties by a suitable prefix. As we speak of fluor- 

 apatite and chlor-apatite, so we can distinguish hydro-herderite, 

 fluor-herderite, if the pure compound is ever found, and for 

 the isomorphous mixture of the two, hydro-fluor-herderite. 

 The axial ratios and other physical properties vary with the 

 composition and the results which have been given in the 

 course of this article will serve as an additional contribution 

 to our knowledge of the isomorphism of fluorine and hydroxyl. 

 The following is a list of the twenty-nine forms which have 

 been observed on the different varieties of herderite, the 

 accompanying letters signifying the prominent localities : 

 A. Auburn, E. Ehrenfriedersdorf, P. Paris, S. Stoneham and 

 G, Greenwood. The relations of these may be seen by refer- 

 ence to the spherical projection, fig. 13. 



Pinacoids. Pyramids., 



a, 100, i-l E. P. r , 112, -4 A. P. 



b, 010,. .« A. P. S. G. *>, ni,-l E. S. 



c, 001, O A. E. P. S. q , 332, -f A. P. S. 

 Prisms. 71, 331,-3 A. E. P. S. G. 



m, 110, I A. E. P. S. G. 0, 441,-4 E. 



I, 120, i-2 S. G. k, 122, -1-2 P. 



}X, 130, i-3 S. to, 3-12-4, -3-4 P. 



Ortho-domes. -p j 131, —3-3 S. 



d, 101,-1-1 S. V '\ 131, 3-3 S. 



e, 302, -§-* A. P. S. G. q, 332, I P. S. G. 

 e, 302, j-"* S. "> 331, 3 A. S. G 

 b, 301, 3-1 A. 5 , § 6 4 5 |-2 G. 

 Olino-domes. V, 121 2-2 G. 



u, 011, \-l S. G. x § 62 3_ 2 S. 



t, 032, fi A.E.P.S. ' g ' ^ p 



V, 031, 3-1 A. PS. Z} t > ^ 



s, 061, 6-1 E. P. S. P, 39l > 9 " 3 G - 



As regards the localities where this rare mineral is found, 

 those in Maine are all within a few miles of one-another, 

 Greenwood, Hebron, Paris and Stoneham being in Oxford 

 County while Auburn is an adjoining township in Andros- 

 coggin County. These localities have something in common 

 with the only other known one for herderite, the tin mines of 

 Ehrenfriedersdorf in Saxony, since both are regions of granites 

 and gneisses, and the mineral occurs associated with cassiterite, 

 topaz and beryl in both cases, 



As regards the position of herderite in a natural system of 

 classification it seems most closely related to the monoclinic 

 wagnerite-triplite-triploidite group. Although a close relation 

 can be seen between the a and b axes the relations of the verti- 

 cal axes and of the inclination /9 are not so clear. 



