If you have access to petrographic thin sections, cross polarisation yields vivid, changing, kaleidoscopic colours worthy of a 60s light show: https://www.shutt

If you have access to petrographic thin sections, cross polarisation yields vivid, changing, kaleidoscopic colours worthy of a 60s light show: https://www.shutterstock.com/shutterstock/photos/395356066/display_1500/stock-photo-thin-section-of-a-olivine-xenolithe-in-basalt-under-cross-polarized-light-395356066.jpg https://www.shutterstock.com/shutterstock/photos/395356066/d... If you don't, the machinery (and space to set it up) may set you back more than $35: https://www.lakeheadu.ca/sites/default/files/uploads/3143/geoprep.pdf https://www.lakeheadu.ca/sites/default/files/uploads/3143/ge... (cheap but large) https://www.wardsci.com/store/product/8877688/ingram-ward-compact-combination-thin-section-saw-grinder https://www.wardsci.com/store/product/8877688/ingram-ward-co... (small but spendy) [In the opposite direction, I once bought a USB microscope and discovered that, when focussed at infinity, it turned into a webcam without an IR filter.] Lagniappe: https://www.youtube.com/watch?v=ncHctrAluLM https://www.youtube.com/watch?v=ncHctrAluLM