One of the unknown samples, labeled Sample X, was able to scratch all the other samples in the lab. What is the likely identify of Sample X?

A mineral that scratches another mineral is harder than the one it scratches. Quartz has a Mohs hardness of about 7, greater than feldspar (about 6), hematite (about 5–6), and mica (about 2–3). Therefore, quartz is the likely identity of Sample X.

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