prize9-2, Exercise 3: A two-question field key

Model answer (check the details):

Q1: Are the grains or crystals separate and cemented, often with layers or fossils? If yes: sedimentary.
Q2 (if no): Are the minerals in bands or sheets? If yes: metamorphic (foliated). If no: igneous (or non-foliated metamorphic).

Misclassifies: marble or quartzite (non-foliated metamorphic), which have interlocking crystals and no banding, so the key would call them igneous. Also, tightly cemented sandstone can look like quartzite.

Care: a field key narrows options; a hand lens, acid test and context confirm the answer.