RIP Tom Krogh

Professor Tom Krogh died late last month. He was the father of modern zircon U/Pb geochronology, and his contributions are easier to illustrate than to tell.

In 1970, when he started working on the U/Pb system in zircon, the smallest single zircon grain that could have its age determined was about this size:


As a result of professor Krogh’s achievements, grains considerably smaller than the ones below can now be analysed using solution chemistry.


But size isn’t everything. He also pioneered chemical and physical abrasion techniques for removing the metamict portions of zircons, allowing the resulting material to be dated more accurately due to the elimination of isotopically open material.

As one of my old bosses said, though, “He wasn’t just good. He was one of the good guys.” While the business of geochemistry can sometimes be secretive, possessive, and petty, Krogh acted in the interest of science. We are all better off as a result.

His son has set up a remembrance page here.