The particular name of an igneous rocks consisting of minerals is best determined using the chart in the lab book and noting:. (a) the presence of quartz and one other mineral.
(b) the presence of vesicles (gas pockets) in proportion with the presence of the mineral quartz.
(c) the relative color (light, intermediate, or dark) and the relative size of the minerals (phaneritic/aphanitic).
(d) whether the minerals present are metallic or non-metallic and then determining the streak on each mineral present.