12 



perceptible undulations, whence the lustre), or crooked *, 

 somewhat jagged, with a few flattish fragments. The cross 

 fracture is nearly at right angles with the stride, with a 

 compact splintery dull surface, seldom in the direction of 

 the strata, which are rarely quite at right angles with the 

 striae. It is much of the same hardness with the crystallized 

 carbonate of lime, does not scratch with the nail, is brittle, 

 and breaks most readily in the direction of the striae. 



Mr. H. Pepys junior seems first to have described this 

 mineral in the Philosophical Magazine, vol. 1%. p. 3645 and 

 according; to his analysis it contains, 



Carbonic acid - 47*600 



Lime - - 50*080 



f Iron - - - - 013 



Loss or water of crystallization - 2*308 



100*000 

 Spec. grav. 2*709 to 2*721. 



It has been formed into snuff-boxes, and turned into studs^ 

 which look very pretty. 



The blackish clay and metallic lustre of the pyrites give 

 it a pretty relief; the top is an example of a septarium of 

 some authors. The rosy blush is a very dilute iron stain. 



* I have a specimen with the striae curved like the Italic f, and the 

 fracture nearly at right angles with every curvature. 



t The iron need not be reckoned, as Mr. Pepys observed it was ad- 

 ventitious, pieces having been chosen quite free from iron. 



