If you have access to petrographic thin sections, cross polarisation yields vivid, changing, kaleidoscopic colours worthy of a 60s light show: <a href="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" rel="nofollow">https://www.shutterstock.com/shutterstock/photos/395356066/d...</a><p>If you don't, the machinery (and space to set it up) may set you back more than $35: <a href="https://www.lakeheadu.ca/sites/default/files/uploads/3143/geoprep.pdf" rel="nofollow">https://www.lakeheadu.ca/sites/default/files/uploads/3143/ge...</a> (cheap but large) <a href="https://www.wardsci.com/store/product/8877688/ingram-ward-compact-combination-thin-section-saw-grinder" rel="nofollow">https://www.wardsci.com/store/product/8877688/ingram-ward-co...</a> (small but spendy)<p>[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.]<p>Lagniappe: <a href="https://www.youtube.com/watch?v=ncHctrAluLM" rel="nofollow">https://www.youtube.com/watch?v=ncHctrAluLM</a>
At $35, it is much less expensive than I anticipated. Still interested in seeing third party reviews.<p>A couple years ago I got a phone camera lens kit in hopes of augmenting my cellphone photography and it was less than stellar.