The commonest hornblende is dark brown barkevicite.
The rocks are liparites, dacites, hornblende and pyroxene andesites.
The gneiss is mostly grey, but occasionally pinkish, its essential constituents (felspar and quartz) being almost always associated with dark mica (biotite) and hornblende in variable quantity.
Red and grey sandstones, hornblende and argillaceous schist are found in the mountains, porphyry and basaltic rocks also occur; sulphur and fuller's earth are worked.
Quincy granite takes a very high polish, owing to the absence of mica and to the coarser cleavage of its hornblende and augite.
It is, however, a hornblende granite and does not possess the mineralogical composition of the syenites of modern petrology.
Along with these, similarly, hornblende and diabase occur in the Pelew Islands and gneiss and mica 1 These are dependencies of New Zealand, as are also the following islands and groups which lie apart from the main Polynesian clusters, nearer New Zealand itself: Antipodes Islands, Auckland Islands, Bounty Islands, Campbell Islands, Chatham Islands, Kermadec Islands.
At Inverell in New South Wales a diamond (1906) has been found embedded in a hornblende diabase which is described as a dyke intersecting the granite.