230 JOURNAL OF THE PLYMOUTH INSTITUTION. 
This Ernesettle rock contains a good deal of brown and strongly 
dichroic hornblende, occasionally patched by viridite, augite, 
particles of ilmenite, and a little mica, It also contains plagioclase- 
felspar. Its closest alliance is apparently with the Weard variety. 
4. Diabase.—The greenstone of Rock and Estover is really 
green, and has a very handsome appearance on a polished face, light 
green mottlings contrasting with the dark. It is chiefly felspathic, 
and the base contains numerous lath-shaped crystals, some of 
which are plagioclase, but which generally have undergone con- 
siderable alteration. There is also augite, well developed, ilmenite, 
and pyrites, and a group of greenish minerals resulting from the 
decomposition of olivine—viridite, chlorite, and in larger quantity 
serpentine. Professor Bonney suggests the former presence also 
of enstatite. The rock is now a diabase ; it is most altered on its 
borders. 
The large intrusive mass which occurs on the north of the 
Yealmpton limestone, and to the action of which upon the latter 
the beautiful green colour of the marble of that locality is probably 
due! (some of the slate has been turned into ‘ porcelain-jasper ”), 
has many points of resemblance to that of Rock and Estover. The 
felspar crystals are not so pronounced, but -plagioclastic characters 
are more distinct. There is not so much pyrites or ilmenite, but 
alteration products occur much as in the other, and there are 
granules of augite with apparently a little olivine. This also is 
now a diabase. (A rock at Park House, Dartington, belongs to 
the same group.) 
A boss at Yarnham, near Modbury, the broken joints of which 
have yielded considerable quantities of asbestus, differs from every 
other rock in the district.? It is dark, hard, fine-grained, and 
compact. It contains an abundance of magnetite and some 
pyrites, skeleton felspars, small granules of augite, and bands 
of yellowish-green epidote. Once a basalt, this too is now a 
diabase. 
Epidote is one of our rarer minerals, and was not recorded as a 
Devonshire species, except microscopically, until identified in the 
Yarnham rock. There is a thin band of igneous rock intruded 
1 Some of the limestone on Stonehouse Hill has assumed a green tinge in 
contiguity to the lava flow there. 
2 Fragments much resembling it occur on the beach at Seaton mouth. 
