Plagioclase:
Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more properly known as the plagioclase feldspar series (from the Ancient Greek for “oblique fracture”, in reference to its two cleavage angles).
Seen in “Moon-dust cake mix shows moon may have had water from the start“, by Andy Coghlan, NewScientist (3 December 2016):
Only when water was included in the mix, at levels of just 0.5 to 1 per cent by weight, did the types and amounts of rock formed match those that have been observed on the moon.
Most importantly, the water-based mixture generated a layer of plagioclase – the main component of the crust – that when extrapolated to the moon would be around 34 to 43 kilometres thick, matching the average thickness measured with satellites. Dry mixtures led to a plagioclase layer twice as deep. This suggests that the moon’s current geology could only have evolved if water was there at the outset (Nature Geoscience, doi.org/btz8).
