160 Notice of Minerals from New Holland. 



nearly of the size of the last figure, are of a grayish white color and 

 nearly opake ; the smaller are colorless and transparent. These 

 crystals are highly axotomons, the folia separating with great 

 readiness parallel to P, and the faces of this cleavage present a 

 high pearly lustre, though not superior to that of sonne of the 

 faces of crystallization in the same direction. Faces M, M vit- 

 reous, some smooth and shining, others roughened and dull. Fa- 

 ces a, a of the pyramids, with few exceptions, perfectly smooth 

 and brilliant, pearly. The proportion between the length and 

 breadth of these crystals is variable ; but in the smaller and most 

 perfect ones it is not less than four to one. 



The other crystals of apophyllite alluded to, are of greater di- 

 mensions, measuring frequently an inch through the vertical axis 

 of the prism. They are derived from a square prism, scarcely 

 distinguishable, in the comparative length of the lateral and basal 

 edges of the crystal, from a cube, and present only simple re- 

 placements on the solid angles, by perfectly smooth and brilliant 

 planes of a high pearly lustre, resembling specimens in the wri- 

 ter's collection from Iceland.* The lateral faces are frequently 

 composed of curved laminae ; and the mineral sometimes presents 

 compound varieties, consisting of lesser individuals, flattened or 

 compressed, so as to show only portions of their planes, or sec- 

 tions of smaller crystals, which have been prevented, by their 

 mutual contact, from assuming their full and perfect proportions. 

 These are united by similar parts, so as to have their similar faces 

 in parallel position with each other. The surfaces of several of 

 the larger crystals are free from these combinations, having bright 

 polished planes, measurable by the common goniometer. The 

 amygdaloid to which they are attached, abounds in vesicular cav- 

 ities, some of which are filled by green earth and hollow nodules 

 of chalcedony. 



Heulandite. (Hemi-prismatic Kouphone- '^' ' 



spar, M.) — The individuals of this species pre- 

 sent the primary form, replaced on the obtuse 

 solid angles by very minute scalene triangular 

 planes, resembling the subjoined Fig. 5, and 



* I have in my possession, (obtained in Nova Scotia last year,) several large trans- 

 parent crystals of this mineral, some of which are replaced on the solid angles by 

 three planes, as in the case of analcime ; a modification which I do not find men- 

 tioned as having before been observed in the crystals of this species. 



