14 PHYSIOGRAPHY. CLASS n. 



Lustre metallic. Colour pure lead-grey. Streak 



unchanged. 

 Rather sectile. Hardness = 2-5. Sp. Gr. = 7'568, 



of a cleavable variety. 



Compound Varieties. Twin-crystals : face of 

 composition parallel, axis of revolution perpendicu- 

 lar to a face of the octahedron. The individuals 

 either terminate at the face of composition, or they 

 reach beyond it, and arc often compressed in the 

 direction of the axis of revolution. It is found at 

 Kapnik in Transylvania. Reticulated, tabular, 

 and some other imitative shapes, the individuals of 

 which are often still observable. Massive : com- 

 position granular, of various sizes of individuals, 

 sometimes impalpable. In this case the colour be- 

 comes pale or whitish lead-grey, the fracture even, 

 or flat conchoidal, and the streak shining. The 

 granular particles of composition sometimes become 

 elongated or compressed in one direction, and then 

 approach to columnar or lamellar ones. Pseudo- 

 morphoses of rhombohedral Lead-baryte. Plates, &c. 



OBSERVATIONS. 



I. The substance, called Blue Lead is generally separated 

 from the species of hexahedral Lead-glance, and considered 

 as a species of its own. The varieties of it, however, are 

 nothing else but the form of rhombohedral Lead-baryte, 

 filled up with the substance of hexahedral Lead-glance, 

 sometimes in pretty coarse granular compositions, as in 

 the varieties from Poullaouen in Brittany, sometimes quite 

 compact, as in some of those from JZschopau in Saxony. 

 The Blue Lead from Cornwall sometimes shews composi- 

 tion. The remainder of the species has been divided into 



