This plugin for ImageJ was created and made available by Terry Ball (Brigham Young University). It can be used for morphometric analyses on phytoliths.
See this study for an example:
Terry Ball, Welmoed Out, Rand Evett, Jammi Ladwig, and Monica Tromp. 2017. Morphometric analysis of phytoliths: recommendations towards standardization from the International Committee for Phytolith Morphometrics. https://doi-org.lama.univ-amu.fr/10.1007/s00334-015-0551-x