Highly crystalline zircon grain from a tropical soil (podzol) developped from a sedimentary kaolin (Manaus area, Brazil). Note the abrasion features on the eges. They are related to transport before sedimentation and evidence the resistance of zircon to dissolution.
Reference: Balan, E., Neuville, D.R., Trocellier , P., Fritsch, E., Muller, J.-P., Calas, G. Metamictization and chemical durability of detrital zircon. American Mineralogist, 2001,86, 1025-1033.