the red rock was red stone, used for wires and electricity (mostly for doors and traps and stuff)
the blue spotty stuff was diamond, which is usefull for practically everything, swords, armor, pics, shovels.
EDIT: and ya, what theMajor said, i didn't notice that part of your post. You have to use an iron pick to mine gold,diamond, redstone, and obsidian. Although i would never try to mine obsidian without a diamond pick.