It may be less critical when you're looking huge coarse crystals, but still equally important is looking at the crystals' host rock, where the individual minerals may not be so big and obvious. And why worry about the "matrix"?  Because understand the host rock, and one better understands the kinds of minerals one might find. Some of the critical tests include checking feldspars for evidence the "albite"-type twin lamellae indicative of plagioclase, and checking small dark ferro-magnesian minerals for the nature of cleavage, if any (amphibole vs pyroxene).

Camera, to document its appearance and orientation in situ.