Ok so how about making it possible to extract trace elements from differnt kinds of stone, Say there where 7 kinds of stone, red colored stone has traces of iron in it, white has tin in it, green has copper, etc. Also they could only spawn in at the correct depth like ic2 ores but at much greater quantities. rich deposits only occour in the propper biomes. rich deposites can be crushed and smelted. The color of the stone should not be obvious at a distance, I am thinking close to regular stone. Using the hammer to determine what kind of stone it is.
Now the method of extracting these elements depends on what you use to process it, you can't smelt the stone into an nuget simply because there is not enough in it. So you have to disolve the stone using acids or other methods ie. in an amalgam of gold and mercury.
using an acid to extract elements should avoid real life technical terms, so water mixed with sulfur and heated makes sulfic acid. A quick look around the web says an acid plus a metal makes a salt. So just call it "iron salt water" or something blatantly simple. So you mix lots of crushed rock into a tank bucket or test tube, Next you could extract the salt water and electrolize it to get metal dust.
1. Certain stone has differnt trace elements
2. Trace elements are tier based, "iron , tin and copper are 1, gold is 2, platinum is 3, chrome is 4 and iridium is 5"
3. Extracting differnt elements take differnt methods
4. The higher the tier the rarer and harder it is to isolate
5. Expand prospecting tools
6. Build ore lab "don't burn your fingers"
Sorry but I could not finish this post in time