**Reynolds Cup 2026 – Registration Announcement**  Registration is now open for the 13th biennial Reynolds Cup, a competition in quantitative mineralogical analysis with an emphasis on clay mineralogy. Participation is open to all and is free to enter via the following link [https://www.clays.org/reynolds-cup-2026/](https://www.clays.org/reynolds-cup-2026/ "https://www.clays.org/reynolds-cup-2026/") .   A total of 100 sample sets, each containing three mineral mixtures typical of clay-bearing rocks, will be distributed on a first-come, first-served basis. Only one entry per organisation is permitted. Participants must submit their analytical results by the forthcoming deadline (to be announced). Those unable to participate are required to return unopened samples, as soon as possible, to remain eligible for future events. A waiting list will be maintained for reallocated samples.  Results will be published for the winner and the top three participants; all other names will remain confidential. Please note that deadlines and result announcements may be adjusted due to shipping delays.  The Reynolds Cup provides an objective platform to evaluate the accuracy of quantitative mineralogical analysis methods. Participation is encouraged for all interested parties.   Further details, including guidelines and previous winners, are available at [https://www.clays.org/reynolds.html](https://www.clays.org/reynolds.html "https://www.clays.org/reynolds.html") . Reynolds Cup 2026 Organizers  **Mark Raven** \ Honorary Retired Fellow\ Diffraction, Mineralogy and Geochemistry \ Mineral Resources E [Mark.Raven@csiro.au](mailto:Mark.Raven@csiro.au) P +61 8 8303 8497 M 0438 988 533 \ CSIRO Mineral Resources, Entrance 4, 40 Waite Rd, Urrbrae, SA 5065\ CSIRO Mineral Resources, PO Box 200, Glenside SA 5065, Australia Deliveries: CSIRO Mineral Resources, Entrance 5 40 Waite Road, Urrbrae SA 5065\ <http://people-my.csiro.au/R/M/Mark-Raven> \ [www.csiro.au](http://www.csiro.au/) CSIRO acknowledges the Traditional Owners of the land, sea and waters, of the area that we live and work on across Australia. We acknowledge their continuing connection to their culture and we pay our respects to their Elders past and present.