"Mineral" is either a noun or an adjective. Example as a noun: Calcite is a mineral. Example as an adjective: "Still in matters vegetable, animal, or mineral, I am the very model of a modern major general" (from The Pirates of Penzance).
Minerals is a noun. It's the plural form of mineral.
part of speech
The part of speech for this particular word is a noun.
what part of speech is beneath
adverb
what part of speech is work
the part of speech sashay is a averb
Did is a verb, and not is an adverb. Didn't is not any part of speech. It's a contraction of did and not.
The word speech is a noun.
Adjective
No, but it's part of a noun which the noun is the part of speech.
Minerals are part of the food that we eat.
Minerals are part of the food that we eat.