Is a diamond a gem or an ore?

Diamond is a gem, it is also the hardest natural mineral on earth. Only about 20% of all diamonds mined are classified as gems, the remaining percentage is used as industrial material to enhance hardness and precision.

The definition of ore according to Merriam Webster reads:

"...a naturally occurring mineral containing a valuable constituent (as metal) for which it is mined and worked, and a source from which valuable matter is extracted."

Diamonds occur in their raw state as solid rocks from which their base mineral -- carbon -- cannot be extracted. Yes, diamonds are mined, and in 'working' diamonds, a diamond cutter removes part of the rock, in shaping, faceting and polishing the gem stone.

A raw diamond looses about 60% of its weight in order to transform it into a gem. No other ore is processed in this way.