Friday, July 09, 2004


Coarse- to fine-grained, rather dark-coloured, intrusive igneous rock that occurs in sills (tabular bodies inserted while molten between other rocks), dikes (tabular bodies injected in fissures), and irregular masses and is always altered to some extent. It consists primarily of plagioclase feldspar, analcime, and titaniferous augite, with barkevikite, nepheline,