What part of speech is “sand”

sand is a common noun that specifically references a fine-grained granular material consisting of mostly composed of tiny grains of rock or mineral particles. Sand is often found on beaches and is used for a variety of purposes such as making concrete or creating art.

1. The sand felt warm against my feet as I walked along the shore.

2. I purchased a bag of sand from the store to fill our sandbox.

when used as a noun, 'sand' should be used in its uncountable form and thus does not normally take a plural form; however, in some cases, a plural form of 'sands' would be acceptable to refer to different types of sand. For example, 'he collected samples of several different sands.' Additionally, 'sand' is often used in compound nouns such as 'sandpaper' and 'sandcastle'.