Short answers, pulled from the story.
The mineral calcite forms the backbone of limestone, appearing as a crystal structure that defines the rock's identity. Skeletal fragments from marine organisms like foraminifera and coralline algae often contain high-magnesium calcite.
Living organisms drove the formation of most limestone deposits over the last 540 million years. Cyanobacteria colonies known as stromatolites built mound-shaped structures in ancient seas by trapping carbonate sediments.
Robert L. Folk developed a classification system emphasizing detailed grain composition and interstitial materials. His method uses two-part names like oosparite to describe rocks with ooids and crystalline matrix.
The Samulá cenote in Valladolid, Yucatán, Mexico represents one such dissolution feature formed by groundwater mixing. Most cave systems exist entirely within limestone bedrock due to this solubility factor.
Kingston, Ontario, Canada earned the nickname Limestone City due to the prevalence of buildings constructed from local stone. Indiana limestone from Bloomington has long supplied high-quality quarried blocks for famous buildings in London.