A Practice Note that discusses the exemption available in transactions under the Hart-Scott-Rodino (HSR) Act involving acquisitions of carbon-based mineral reserves. This Practice Note discusses the Rule 802.3 exemption that applies to reserves of oil, natural gas, methane, shale, or tar sands, and coal, and associated exploration and production assets, such as equipment and machinery. This Practice Note also covers how to determine when the exemption applies and the effect of the exemption on the HSR size-of-transaction.