72 TROCEEDINGS OF THE ACADEMY OF [1883. 



A paper entitled " On the mutnal relations of the Bunotheriau 

 Mammalia," by Edw. D. Cope, was presented for publication. 



Crystallized Serpentine from Delaivare. — Professor H. CARvrLL 

 Lewis remarked that a short time ago, his venerable friend, Dr. 

 Isaac Lea, had handed him for examination a specimen of Deweylite 

 from Way's feldspar quarry, near Wilmington, Delaware, upon 

 which were some crystals of an unknown micaceous substance. 



The white, waxy deweylite, weathering to a pale yellow color on 

 the surface, contains numerous angular fragments of transparent 

 quartz, which vary in size from microscopic dimensions to frag- 

 ments two inches long b}^ one-half inch wide. In all cases these 

 fragments are perfectly sharp and are generally rhomboidal in 

 shape. These rhombic cleavage fragments are just such as would 

 be produced by throwing a heated crystal of quartz into cold 

 water. Under the microscope, the quartz is shown to contain 

 hair-like raicrolites and minute oval cavities, the major axes of 

 which are usually placed in one direction.^ 



The deweylite also contains irregular masses of feldspar ( albite), 

 which are more or less altered into deweylite. Unlike the frag- 

 m.ents of quartz, these feldspar nodules are almost invariabl}'^ 

 rounded in outline, as though partially dissolved away The 

 feldspar has lost both its lustre and its hardness. It has a waxy 

 appearance, and its hardness is reduced to 4*5. In some speci- 

 mens one end is more altered than the other, and it is evident that 

 the deweylite is the result of the alteration of albite. 



The third mineral in the deweylite is in the form of plates or 

 crystals of a micaceous substance of a pale smoky pearl color with 

 a faint greenish tinge. The plates may be several inches in diam- 

 eter, and are traversed by numerous joints or cracks filled with 

 deweylite, which are generally inclined to one another at angles 

 of 60-" and 120°. The crystals appear to be sections of an ortho- 

 rhombic crystal, bounded by six prismatic planes, whose angle of 

 intersection is 120°. In the polariscope, the mineral is seen to be 

 doubly refracting, and is biaxial with a small optic-axial divergence 

 (probably between 10° and 20°), the hyperboles being indistinct. 



It has a strong pearly lustre, an eminent basal cleavage, almost 

 micaceous, and is brittle. It has a hardness of 2'5, and specific 

 gravity of 2'4l. It is translucent, and by transmitted liglit is 

 grayish or greenish yellow. 



In the closed tube it gives oflT water and decrepitates slightly, 

 becoming blackish gray or dark steel-colored. In the blow-pipe 

 flame it blackens, then turns white, exfoliates slightly and fuses 

 with boiling at 4-5 to a white bead. In the salt of phosphorus 

 bead it dissolves completely to a clear glass which becomes milk- 

 white in a cold saturated bead. With cobaltic nitrate on charcoal 



' V. Further notes on inclusions in gems Isaac Lea, Proc. Acad. Nat. Sc. 

 Phila., May, 1876. 



