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Creamy Basanite

This almost quadrate cushion Basanite shines like a juicy caramel. An unusal gemstone in a medium size usable to both a ring or a pendant, or even a brooch. (Note! The colour is darker than in this picture, it can also vary slightly due to screen calibration)

 

Size: 24x25 mm

 

Origin: Afrika

 

In stock:  1

 

Price:    USD 11.20

 

Basanite is an igneous, volcanic (extrusive) rock with aphanitisk to porphyritic texture and belongs to the jasper family. Minerals are usually abundant unit feldspathoid (nepheline or leucite), plagioclase and augite with olivine and less concentrations of iron-titanium oxides such as magnetite and ilmenite-ulvospinel; minor alkali feldspar may be present. Clinopyroxene (augite) and olivine are common as phenocrysts and in the matrix. The augite contains significantly greater titanium, aluminium and sodium than that in typical tholeiitic basalt. Quartz is absent, as are orthopyroxene and pigeonite.
Basanite occurs both on continents and islands. For example, together with basalts, they are produced by hotspot* volcanism in Hawaii and the Comoros.


* Hotspots are volcanic regions thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle. They may be on, near to, or far from tectonic plate boundaries. Currently, there are two hypotheses that attempt to explain their origins. One suggests that they are due to hot mantle plumes that rise as thermal diapirs from the core-mantle boundary. An alternative hypothesis postulates that it is not high temperature that causes the volcanism, but lithospheric extension that permits the passive rising of melt from shallow depths. This hypothesis considers the term "hotspot" to be a misnomer, asserting that the mantle source beneath them is, in fact, not anomalously hot at all.

 

 

 

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Latest update: 28 augusti 2015