Thanks so much for putting all this information together and collecting most of the FAQ from the comments section! Here are a few extra details you can add, along with some updated info. These are extremely spoilery, so new players should avoid reading further:
Resource spawns:
Quartz: Soil, Sand, Hard Soil, Mud, Stone, Ice
Copper: Soil, Hard Soil, Mud, Stone
Iron: Mud, Stone
Gold: Stone, Granite
Titanium: Granite, Magma
Coal: Hard Soil, Stone, Granite, Magma
Amethyst: Sand, Ice
Emerald: Stone
Ruby: Ice, Granite
Sapphire: Ice, Magma
Diamond: Granite, Magma
Some additional info:
Cow spawns after 100 digs downward
Wood spawns after 120 digs in any direction
It's technically possible to reach higher than 13 Power using Fern + Lumen Pickaxe, but it would require extremely good rng with restore cells, so it's very unlikely
Encased Relics start to spawn after Lorestone has been unlocked and only spawns after 100 depth with increased spawn rates at 200 and 350 depth respectively
Scoot's Theme is unlocked when you have collected the Scoot's Groove Disc relic