Purple Haze - The Jimi Matrix Experience
by Grace Shephard, Centre for Earth Evolution and Dynamics (CEED), University of Oslo, Oslo, Norway
Rhomb porphyry is a type of igneous rock filled with wedge-shaped phenocrysts of orthoclase (K-feldspar) in a fine-grained silicate matrix. It is often described as a rare rock type as it is only known at three localities; the East African Rift, Mount Erebus in Antarctica and, as shown here, near Oslo, Norway. In the Permian (from around 290 Million years ago) the Oslo fjord region underwent a dramatic volcanic and rifting event which saw voluminous lava flows and volcanic deposits. The term porphyry is from Ancient Greek (πορφύρα porphúra) and means "purple" - which is certainly the case for these beautiful pebbles.
Grace Shephard (distributed via imaggeo.egu.eu)