Nice ending. They present this mentor/coming-of-age/let's learn science thing really well with a layer of yuri subtext throughout. The skinship Ruri and Nagi have, the way Ruri behaves like a total brat with her right away bossing her around, the way Nagi looks at her with those adoring eyes, their special moments throughout like picrel, it's all really nice. The height gap is phenomenal, the author really has a special fetish that I very much appreciate. They actually made me like mineralogy.
This will go in my tier of precious heavy subtext shows together with Sorairo Utility and Days at the Breakwater. Do it yourself is stronger than these, feels borderline text so it's in a category of its own I guess.