Norman L. Bowen discovered the crystallization sequence that produced most of the rock-producing minerals. Known as the Bowen Reaction Series, he was the first to reproduce plagioclase.
Plagioclase
CaAl2Si2O8 (An)- NaAlSi3O8 (Ab)
A well-shaped crystal in an igneous rock needs room and time to grow. So, minerals with high melting points form well shaped crystals while ones with lower melting points don't because there isn't as much time for them to form. Quartz crystallizes at a lower temperature than plagioclase so plagioclase is more likely to form well-shaped crystals.
One physical property that distinguishes plagioclase feldspars from orthoclase feldspars is their cleavage. Plagioclase feldspars typically exhibit good cleavage in two directions at right angles, while orthoclase feldspars show perfect cleavage in one direction. Another distinguishing feature is their color. Plagioclase feldspars are usually white to gray, while orthoclase feldspars can be white, pink, or other colors.
plagioclase feldspar & hornblende
Olivine... if you can find on the internet the "Bowens Reaction Series" paper, it will tell you that Olivine is the first to crystallize
Plagioclase.
No. The chemical formula of Plagioclase feldspar is (Na,Ca)(Si,Al)4O8
Plagioclase and Hornblende
Plagioclase
Plagioclase is not actually a rock, but a member of the feldspar family of minerals, and a major rock forming silicate mineral.
Yes. I even have a specimen of it.
Plagioclase
Diorite
CaAl2Si2O8 (An)- NaAlSi3O8 (Ab)
quartz will have conchidal fracture...plagioclase will have 2 sets of cleavage near 90 degrees and some striations quartz will have conchidal fracture...plagioclase will have 2 sets of cleavage near 90 degrees and some striations
quartz, plagioclase and alkali feldspars