The goal of this project is to develop novel proppant and reservoir tracer particles based on natural materials (e.g. large bee pollen, walnuts and other hollow particles) which have spectrally encoded identities. The concept is to modified abundant, naturally occurring and low-cost particles to contain resin shells with unique spectrally encoded signatures for use in hydraulic fracturing and reservoir monitoring. The particles will be hollow to avoid sedimentation and enhance flow behavior. The codes will designed with rare-earth upconverting nanocrystals (UCNs) which can withstand the harsh temperatures seen underground, be manipulated with magnetic fields, and be read out in a complex solution environment when recovered.