If the minerals are too small to be readily identified by the naked eye, then color is used for the extrusives.
(the minerals; are then; too small to be readily identified by the naked eye) (the minerals; to be readily identified; by the naked eye) (color; is used; for the extrusives)
the minerals the minerals color
are then to be readily identified is used
too small to be readily identified by the naked eye
by the naked eye
for the extrusives