Titanium

Titanium is a ore only found at layers 5 and under (bedrock layer), but it is a very stong metal. It can be used to create many alloys: Dusksteel, Hyperium, Ignisium, Composite, and Pyregold are good examples.

Titanium Tools
Titanium tools have 1,750 uses, which is about 200 more then diamond. However, it has the speed of gold, which is handy if you want a full scale mining operation.