Approximately 50 years ago my hobbies were rockhounding (hunting for minerals) and cave exploring. Sometimes the two got combined, when I encountered various interesting minerals inside a cave. I clearly remember seeing a large broken piece of Calcite. Your mystery-rock appears to have the same cleavage and fracture-pattern as the Calcite specimen I found in that cave. By the way, Calcite's color can vary, from almost like glass to honey (including dark honey) according to how much dissolved iron got mixed in when the Calcite crystals were forming.
Do you think your mystery-rock is "native" to the place you found it, or was it possibly carried there (such as, by a gravel- or stone-delivery truck). I'm asking because it's important to know what the Geology of your part of your state is. Calcite forms when Sedimentary rocks were deposited by ancient oceans... not created by fire (Igneous/Volcanic rocks), nor heat/pressure (Metamorphic rocks). For example, the mineral Obsidian (volcanic glass) is not naturally found in Florida, but people have actually found some pieces of Obsidian there because I arrived in a load of gravel.
