What is the difference between resource and reserve in geology?

In the field of geology, the terms “resource” and “reserve” are used to describe different categories of potentially extractable materials. While they are related, there are distinct differences between the two terms:

Resource: A resource refers to the total amount of a particular material that exists in the Earth’s crust, irrespective of its economic viability for extraction at the present time. It represents the known or estimated quantity of a resource within a given area. Resources are often classified into different categories based on their level of geological knowledge and confidence in the estimates. The three common categories are:

• Inferred resource: This represents the lowest level of confidence and is based on limited geological evidence. It refers to the estimated quantity of a resource that is likely to exist but with a low level of certainty.
• Indicated resource: This category indicates a higher level of confidence compared to inferred resources. It is based on more detailed geological information, including sampling and drilling data. An indicated resource represents an estimated quantity of a resource that is more reliable than an inferred resource but still lacks the level of certainty required to be classified as a reserve.
• Measured resource: This category represents the highest level of confidence among resources. It is based on detailed geological information, such as extensive sampling and drilling, providing a higher degree of certainty about the quantity and quality of the resource.

Reserve: A reserve, on the other hand, refers to the subset of a resource that is economically recoverable using existing technology and under current economic conditions. Reserves are the portion of a resource that has been demonstrated to be economically feasible for extraction. They require a higher level of confidence and feasibility studies to determine their economic viability. Reserves are often further divided into two categories:

• Proven (or proved) reserves: These are reserves with a high degree of confidence and are typically supported by detailed geological and engineering data. Proven reserves have a high likelihood of being economically recoverable.
• Probable reserves: This category represents reserves with a lower level of confidence compared to proven reserves. Probable reserves are based on preliminary geological and engineering data and have a lower certainty of being economically viable.

In summary, a resource represents the total estimated quantity of a material, whereas a reserve refers to the portion of that resource that is economically recoverable under existing conditions. Resources provide a broader understanding of the potential, while reserves focus on the economically viable portion