Rock group	Sedimentary
Origin	Chemical
Primary minerals	Calcite Aragonite

Limestone is the protolith of marble.

Limestone in Hand Sample

Helderberg limestone featuring stylolites
Tonoloway limestone
Storm deposits recorded in Tonoloway limestone (one of your friendly author’s personal favorites)
Ulster white limestone featuring a fossil belemnite
Brown limestone
Oolitic limestone
Encrinal limestone
Fossiliferous Keyser limestone
Bryozoan-rich limestone
Tansil Formation limestone with pisolites

Limestone in Thin Section

Thin Section GigaPans

Oolitic limestone, plane polars
Oolitic limestone, crossed polars
Fossiliferous limestone, plane polars
Fossiliferous limestone, crossed polars
Encrinal limestone, plane polars
Encrinal limestone, crossed polars

At the time of this writing, WordPress was being very weird and refusing to embed the YouTube link for oolitic limestone in crossed polars.