What part of speech is as in the sentence hard and sharp flint?

In the sentence "hard and sharp flint," the word "as" is not present. Therefore, it's impossible to determine its part of speech.

It's possible that you meant to ask about a different word in the sentence. For example:

* Hard and sharp are both adjectives describing the flint.

* Flint is a noun.

Please clarify your question if you meant to ask about a different word.