Mica schist is primarily composed of mica, whereas aventurine - note the spelling- is composed of quartz with abundant inclusions of mica. This makes for a relatively hard, tough and attractive...
black mica is biotite which is a phylosilicate containing potassium and iron/magnesium. The silver mica is muscovite which is also a phylosilicate but it contains potassium and aluminum rather than...
Within group differences refers to differences within one individual group. Between group differences refers to the differences between 2 or more groups.