Graham — Pseudomorphs in McGill University Collection. 47 



Art. YIII. — Note on two interesting Pseudomorphs in the 

 McGill University Mineral Collection; by B. P. D. 

 Graham, B.A. 



1. Pseudomorphs of Orthoclase after Laumontite from Templeton, 

 Ottawa County, Quebec. 



The specimens described below were collected some years 

 ago by Dr. B. J. Harrington in the apatite region of Temple- 

 ton, and had been labelled by him as pseudomorphs after lau- 

 montite, although they were not further examined at the time. 

 They consist chiefly of flesh-red to almost white crystals, meas- 

 uring up to about half an inch in length for the most part, 

 and having a very fresh appearance, the edges being quite sharp 

 and the faces smooth with a dull and somewhat waxy lustre, 

 although in some cases they are somewhat weathered on the 

 surface. They are of the usual laumontite habit (fig. 1) show- 

 ing a combination of monoclinic prism with basal i 

 plane. The faces do not directly yield reflections 

 owing to their dull lustre, but by placing a drop 

 of alcohol on each in succession, after adjustment 

 on the reflecting goniometer, and taking readings 

 at the moment when the drop is just about to dis- 

 appear (as suggested by H. T.Whitlock*), the angles 

 can be measured with a fair degree of accuracy, 

 and they were found to correspond with those of 

 laumontite. The crystals are implanted in irregu- 

 lar groupings in a compact material of a rather 

 paler tint, but possessing the same general char- 

 acters, and this in turn encrusts the dark green 

 pyroxene and brownish phlogopite which are characteristic 

 of the Templeton locality. The pyroxene is in the form of 

 large prismatic crystals, an inch or so in diameter, and both 

 this mineral and the phlogopite are more or less completely 

 coated with a layer a quarter of an inch thick of the pale-colored 

 massive material from which the jDsendomorphous crystals 

 spring ; there are also dispersed through it fragments of a 

 pale green apatite, and in one of the specimens, a crystal of zircon. 

 The prism faces of the crystals are usually striated vertically 

 and sometimes exhibit a step-like structure along the directions 

 of the original laumontite cleavages, which, however, are now 

 entirely lacking. The fracture is fairly even, and the crystals 

 are solid and homogeneous throughout ; in physical characters 

 they correspond exactly with the feldspar : H -- 6, Sp. G. = 2*56. 

 Thin splinters fuse B. B., the pink color fading to white ; and 



*N. Y. State Museum Publication, 1905. 



