If you see trophies near you, seize the opportunity and drill that trophy now!
Some people say they have had a hard time finding Iron Ore. Admittedly, it is hard to locate Iron Ore during your first plays. My advice to get iron is upgrade the propeller to MK-3 or Mk-4 (I forgot) and buy fuel (consumable item). After that, go to an aerial planet and fly until you reach 80 altitude and you will see iron there and many more in the 90+ altitude.
You can't drill upward on an aerial planet intentionally. It is not a bug and has nothing to do with drilling power.
You can learn some actual tips about mining from this game! I guess the developer is a mining engineer or has a contact with a mining engineer HAHA...
HAVE FUN WITH THIS GAME AND ENJOY PLAYING.
For Coral Shards, some people say this crystal don't appear neither screen nor mini map. These are found on blocks under 170 that have a red bubbling plant on them.
You are in desperate need of rare crafting materials (like Pearls , Coral Shards , Viscera etc.) AND have the materials to solve an achievement? Go find that material, but DO NOT mine it! Go back to your mother ship and do that upgrades to get the achievements. They will give you bonus time, and bonus time will grant you the double amount, if you mine this material now.
Watch your cargo space. It is especially frustrating to pick up a rare material only to find you had no free space. When you spot something you need while fully loaded, you can free up some of your cargo space on the go by wasting something "to repair"/"to fuel"/"to oxygen" even when said depletable is full.