primary sources

(しりょう) Usually not physical. source material for a novel or a report.
(ざいりょう) Usually seen on the “ingredients” label on food packaging. But also used about source material for a report:field notes, raw data. The implication is that, unlike 素材, the source material is not totally raw, it’s partially assembled –for instance, if you get silk, that’s 素材, but when the silk is woven into a fabric, that is 材料, and then the fabric is an ingredient of a handbag.
(そざい) Raw material – like the related term 材料 but, 素材 emphasizes RAW – iron, brick, mud. Usually used with architecture or industry.