Semi-fossilized or fossilized coprolite, vertebrate organ, or mineral deposit
Unknown excavation source
Unknown age/ era

A possible vertebrate organ. While rare it may be possible, but most likely a mineral of mica or copper. Bones and teeth are usually the only parts that preserve since they are hard and durable. Although rarer, sometimes feather and scale impressions can be preserved. Occasional soft tissue organs are discovered but they are those of aquatic animals and have a different ventricle system. Generally the harder the body part, the greater likelihood of it being fossilized. Specimen is 3. 2" x 3"; with an unspecified weight. I agree, an in-person evaluation will further define the item you have questions about. An in-person assessment with a regional paleontologist or geologist at a university or museum would be able to identify the distinctive features of your example. This assessment could increase the fair market valuation that is given here, especially if the item is discovered to be a mineral deposit. It is important to recognize local, state, and US federal laws and prohibitions of sale and shipment of Fossils and Paleontology items.

Thank you for contacting Mearto with your appraisal inquiry. So that I may best assist you, can you please give more information on where you received this item? How do you know it is a heart? What circumstances brought it to you? What is the weight? If it is fossilized and has the weight of a stone of similar size: I believe it may be coprolite
(fossilized animal waste) or a mineral deposit (possible copper).