The problem with identifying minerals in igneous rocks, particularly when they are small-grained, is their lack of crystallization.
(they; are; small-grained) (The problem with identifying minerals in igneous rocks; particularly is; their lack of crystallization; T:when they are small-grained)
they The problem with identifying minerals in igneous rocks
are particularly is
small-grained
their lack of crystallization T:when they are small-grained