Look for the ore patches via a suit flyover of the area. It's an incredibly effective method to see many ore deposits on planets. I can map out a large number of deposits within minutes that way. For an example do a google image search for "ore patches space engineers". Also, your hand drill detector is low range so there is potential you could even be right on top of ore and not detect it. However, the patch should still show from the air if there is some near. Once you do get a grid based detector make sure it's range is set to what you want as Keen has halved the range by default so you may want to slide the power/range up. My current MP game there was someone on that was looking for 3 days for cobalt and then found it very near to their base. They just didn't know how to look. It took mme three long seesion over a weekend in MP to find cobalt in space. Now I have locations marked all over space. As to starting in the mountains on a planet? Nothing wrong with it. I prefer it in MP for safety and and often easy access to ice if I am on planet. Mining is often best done away from your location anyway at least as far as Multiplayer goes. Mining activity is a dead giveaway to nearby players. Also, since you say you are playing Sandbox as opposed to Survival you can always play in Creative mode OR enable creative tools which will allow you to spawn in anything you need.