What is a type specimen?
A type specimen is the portion of a newly classified meteorite that is deposited permanently in a recognised scientific collection, so researchers can always go back to the original material.
When a new meteorite is described, scientists need a guarantee that the material behind the description will remain available. Collectors sell, trade and cut specimens; private collections are broken up. So the rules for naming meteorites require that a reference sample, called the type specimen, is placed in an approved repository, usually a museum or university collection with long-term curation.
The idea is borrowed from biology, where a type specimen anchors the name of a species. In meteoritics it means that if someone later questions a classification, or a new technique becomes available, there is authenticated material to study. The Meteoritical Society's guidelines set a minimum amount; for most meteorites this has commonly been the lesser of 20 per cent of the total known mass or 20 grams, together with any polished thin section made for the classification. Rules are periodically reviewed, so the classifying laboratory will confirm the current requirement.
Type specimens are not usually the most attractive pieces. They are chosen to be representative, and they are often a cut slice or a fragment rather than a fully crusted individual. Their value is scientific: a type specimen of a rare Martian or lunar meteorite may be studied for decades by teams around the world, who borrow small pieces from the repository.
For a finder or owner, the type specimen is the price of getting a meteorite officially recognised. Giving up part of a stone can feel painful, especially for a rare type, but without that deposit there is no approved name, and an unnamed rock is very hard to verify, trade or study. Many owners also see it as a contribution to science that outlasts any private collection.