Tom Krogh was without a doubt the most influential U–Pb geochronologist of the modern era. His career was marked by a continuing series of breakthroughs, both revolutionary and evolutionary. His legacy is such that every lab around the world uses the methods he developed. After some fascinating insights into chemical leaching effects in zircon, Tom largely dropped this approach in favor of his enormously successful air abrasion technique, coupled with careful sample selection at the individual grain level. Here, I describe continued experiments with leaching and “step-wise dissolution” techniques, and how a series of alternating steps forward and setbacks eventually led to a new “chemical abrasion” or “CA–TIMS” method for selectively removing those domains within zircon that have lost Pb. Continuing to strive for improvements in analytical technique is perhaps the best way to honor Tom’s many contributions and extend his legacy.

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