Possible Speleothem (Cave Rock) Section North America, Colorado, Canyon City Unfortunately, I do not believe this is a biological fossil. Animal soft tissue would not fossilize in a rock formation; though it can sometimes leave an impression on the surrounding matrix it was incased in. I do believe this is an example of mineralization on rock. This tens- of- thousands to hundreds- of- years natural process is a chemical alteration, replacement, and enrichment of minerals within igneous, metamorphic, and sedimentary rocks. The center of your specimen, does appear to be a limestone section; a type of sedimentary rock. As it is a section, and removed from an original position, I cannot state with absolute certainty; but the tapper from one edge to the other makes me think it may be a cave rock formation. A possible stalactite or stalagmite. These are mounds or tapering columns rising from the floor of a cave, formed of calcium salts deposited by dripping water and often uniting with a stalactite at the top of a cave. The most common stalagmites are speleothems, which usually form in limestone caves. the center of your specimen, does appear to be a limestone section. Example 12" x 8"; unknown weight. A possible reason for discovering this section outside of a cave environment would be historic mines in the area. It could have been removed during a small mine excavation. It could also be from a large explosion that expelled the rock from a large detonation made by a larger mining operation (a large company operation, for example). Meeting with an in-person specialist in geology from a regional museum or University may give more information on the example. I was not able to find like items in recent auction results; but do see retail sales of this type of cave rock. Retail price and range are higher and at greater variables than a Fair Market Value assessment. I have given a FMV assessment for your object.
