Dear Clay-friends, (and in this we include anyone interested in quantitative mineralogical analysis of samples that may contain clay minerals!) The 2024 (12th) biennial Reynolds Cup competition on quantitative mineralogical analysis is open for registration.  The competition is open to anyone interested in quantitative mineral analysis, with particular emphasis on clay mineralogy. A sample request form and Information about the competition including guidelines and previous winners can be found at [https://clays.org/reynolds](http://clays.org/reynolds). The competition is free for all to enter, however, those who are not members of the CMS are encouraged (but not obliged) to become members (see <https://clays.org/join_benefits_of_membership.html>).  A total of \~100 sets of samples will be made available for distribution. Each set will comprise three samples of \~3–4 g of mineral mixtures commonly found in clay-bearing rocks. All sets of samples will be distributed in the order of registration.  The top three contestants with the most accurate results will be announced at the 61st Annual Meeting of the Clay Minerals Society (May 2024, Hawaii (dates TBD)). Only the names of the top three contestants will be published. The names of the other participants will remain strictly confidential. Because of the popularity of the Reynolds Cup and the enormous amount of work put into its preparation, potential participants are strongly encouraged to plan ahead and only request samples if they are sure they can complete the analysis and return results to the organizers by the due date. Those who request samples and do not send in results or fail to return the samples unopened WELL BEFORE the due date will not be eligible to participate in future Reynolds Cups. A waiting list will be kept to offer returned samples to other potential participants.  The Reynolds Cup, blind Round Robin is the perfect way (possibly the only way!) to test the ability and accuracy of your methods of quantitative mineralogical analysis, whatever you prefered method or technique, so join the fun and participate. Reynolds Cup 2024 organizers