A71 " Ovensfone" from Zinal, Canton Valais. Ill 



dolerite, and is commonly intrusive, generally as a sill, and that it 

 has been converted into a schist by subsequent pressure and mineral 

 change.^ 



The annexed diagram gives the section seen in the quarry. 

 A is a compact variety of the green schist (descinbed below), forming 

 a cliff some five or six yards high, A' indicating a foot or so at the 



base where the rock is more distinctly fissile ; B, a soft flaky rock, 

 rather like a crushed serpentine, the thickness, which slightly 

 varies, being from about 3^ feet to 4 feet ; C, the " ovenstone," 

 exposed for about 4 feet ; I), a spoil bank. Between B and 

 there is no sharp line of division, the one passing, though somewhat 

 rapidly, into the other. The condition of B made it practically 

 worthless for purposes of study, so I collected specimens from C 

 only, one being slightly more fissile than the other. The dominant 

 tint in each is a lead-grey inclining to a dull lavender, and 

 sometimes, especially on the smooth faces of the more fissile 

 specimen, to a dull green, as in a much crushed serpentine. In 

 both are greenish-white seams more or less parallel with the 

 foliation. The streak also is white, the hardness rather variable, 

 but under 2. Examination with a lens shows numerous glittering 

 granules of iron-oxide rather irregularly distributed, some of the 

 larger being well-developed octahedra, undoubtedly of magnetite. 

 The slice cut from the more fissile specimen exhibits a rather minute 

 wavy, foliated structure, with more definite cleavage cracks running 

 in the same general direction, the dominant mineral varying in tint 

 from a very pale grey to a light brownish grey. It is traversed 

 by rather irregular streaks, like crushed-up veins, occupied by clear 

 1 Quart. Journ. Geol. Soc, vol. l (1894), p. 283. 



