This rock occurs in thick strata, alternating with several of the older Limestones of the central parts of England, and ranks among the Transition rocks of Werner; its basis is a very fine grained Greenstone, being an aggregate of Feldspar and Hornblende: a greater or less proportion of green Talc enters into its composition, giving it a brighter green colour and more earthy texture. The varieties are numerous, but this figure we think sufficient for this work. This is an intermediate variety, it contains much Talc, and has chiefly Carbonate of Lime in the vesicles, arid some small balls of Iron oxyde. The browner and more compact varieties commonly contain imperfect agate, and rarely Zeolite.

The amygdaloids with a basis of Wacke, winch occur in the newer Flætz Strata contain fine Agates, Zeolite, Carbonate of Lime, &c. There are three regular strata of Toadstone, alternating with the Limestone in Derbyshire; from one of these the specimen figured was sent me.