Gem Tools by Mark680
this mod adds tools with special mining modes, armor with potion effects and ores
GemCraft by Sanguine045
Ever think that emeralds are a vastly underimplemented part of the game? well here you go! this mod adds two more types or gemstone (sapphire and ruby) as well as full tool and armor sets for all three types of gem.
Gems+ by RobZ51, microjunk, ahojkaj, Mitrix50, rolfXD, Torzel, Zealot067
Adds lots of gems which you can make tools and armor out of.
Gemtastica/JAMM by TheErik557
Just another mineral mod, more than tools, some decorative blocks and items, and trades