﻿W. E. Hidden — Contributions to Mineralogy. 209 



2. A remarkable crystal of Herder it e. 



The crystal here noticed was found in the early part of 1884 

 at the locality near Stoneham, Me., by Mr. N. H. Perry, but it 

 did not come before me for examination until after the notices 

 of this mineral had appeared. (This Journal, xxvii, pp. 73, 

 135, 229.) Excepting 3-2 (362, x), t*2 (120, T) and i-3 (100, n) 

 all the planes observed on the American crystals occur on this 

 crystal, and one new plane, the unit macrodome, is seen to be 

 present, 1-z (101, d). The pyramid 1 (111, p) is invariably 

 dull and waxy looking on the crystals from Stoneham and for 

 this reason it is distinguished from the other planes. This 



crystal has a diameter through the macro-axis of 25 mm and in 

 point of size and general perfection is unequaled. 



The figures represent this crystal natural size and with the 

 natural development of the planes. Fig. 1 shows it with the 

 brachy-axis placed vertical, while in fig. 2 the position is the 

 normal one. The occurring planes are thirteen in number 

 with several others slightlv indicated, they are: (001, c) ; 

 i-i (010, b); 1 (110); \-l (101, d); %'l (302, e) ; hi (011, u); 

 |-i (032, 0; 3-S (031, v); 6-2 (061, s); 1 (111, p); f (332, q); 

 3 (331, n) and 3-3 (131, y). This American herderite can be 

 readily distinguished by its phosphoresence in the dark when 

 gently heated. It exhibits under this treatment a bright 

 orange-yellow color; amblygonite from the same locality 

 showed a bright lavender-blue phosphoresence. 



The index of refraction for this species has been determined 

 anew by Des Cloizeaux, with results differing from those first 

 announced. He now gives as the mean index of refraction for 

 yellow rays: /3=1*609; this was obtained from a small prism 

 with an artificial face parallel to the base and a second formed 

 by the plane e (302). Mr. Perry has lately found this mineral 

 at the tourmaline locality near Auburn, Me., and a few excel- 

 lent crystals were obtained there. These were announced in 

 the Trans. N. Y. Acad. Sci. for Dec. 7, 1885, by Mr. G. F. 

 Kunz. 



In conclusion I wish to thank Mr. C. S. Bement, to whose 

 cabinet this crystal belongs, for the opportunity of describ- 

 ing it. 



