GreenSpar is a form of the mineral Anorthosite (aluminosilicate), a rare compositional variety of plagioclase feldspar
. It is unique in that it is very dense and has a high refractive index.
Typically, the first to crystallize are two magnesium- and iron-rich minerals (olivine and pyroxene) that are both a little denser than the magma, and sink down through it, then a mineral (plagioclase feldspar
), that is less dense and floats to the surface.
Dominance of plagioclase feldspar
over alkali feldspar is interpreted as being the result of high volcanic input.
In the latest work, Fourier-transform infrared spectroscopy was used to analyze the water content in grains of plagioclase feldspar
from lunar anorthosites, highland rocks composed of more than 90 percent plagioclase.
CHEMIN RESULTS REVEALED: NASA's Curiosity rover gets its first taste of Mars and finds minerals: plagioclase feldspar
, pyroxene and olivine.
Photomicrographs of sandstone of the Loralai Formation: (a) showing highly quartzose nature of the sample, 10x10, XPL; (b) monocrystalline quartz grain (circled),10x10, XPL; (c) polycrystalline quartz grain (circled), 10x10, XPL; (d) perthite grain (arrow) in the centre, 10x25, XPL; (e) plagioclase feldspar
(circled) surrounded by quartz and lithic fragments set in spary calcite cement, 10x40, XPL; (f) back- scattered SEM image showing quartz and authigenic euhedral albite, bar scale shows 20 um.
Just like the rocks on Earth, Moon's have lots of basalt and olivine, pyroxene, and mafic breccias, along with plagioclase feldspar
, also known as anorthosite.