Notes on a collection of igneous rocks from Lord Howe Island
Introduction. The collection comprises about twenty specimens, collected by Mr. R. Etheridge, junr., and Mr. Alexander Morton.
Classification. Allthe hand specimens examined belong to the basalt group. They appear to belong to three leading types: 1. Basalt with olivine. Theseare chiefly dense dark greenish-gray rocks, for the most part little affected by decomposition, some of them probably being of comparatively recent origin.
2. Basalt without olivine, lateritic. Thisis a lateritic rock, of a dull brick-red colour, soft, earthy and amygdaloidal; passing in places into scoria. This lava may be partly submarine.
3. Basalt, diabasic. A hard dense pyritous rock of a greenish-gray colour and resembling an andesitic dolerite; it has undergone extensive alteration, and is probably of considerable geological antiquity.