Opalized Thoughts use to be a famous geologist from Canterlot who specialized in gems.  
His original name was Professor Stone and his parents were highly respected geologists  
He was famous for inventing spells that could be used to make work easier so he could make more money for his family and friends who were his workers.  
He became very short tempered, aggressive and tyrannical because of the deadlines and stress that was a part of his job.  
Came up with a spell that was supposed to create gems to make his life easier but he made a mistake and it backfired.  
The spell covered his horn in his favorite gem, the opal, disabling his magic and buried him and his workers in the cave they were working on.  
The workers made it out but went back to find him, luckily he wasn’t crushed and they dragged him to safety.  
He was in a coma for half a year before he suddenly stopped breathing and they couldn’t revive him.  
Stone’s old friends buried him in the cave where they first found opals and started their business.
 
After the incident  
A year went by and a miracle happened, he woke up!  
He was infected by retrograde amnesia and forgot everything, every memory he had made was gone.  
After some time he was discovered by his old teammates who went to pay respects, but he couldn’t remember them.  
The friends took this as a blessing and treated him just like an old friend. No one ever told him his real name in fear that he’d remember his past and return to being a tyrant, so he made one up that was supposed to symbolize the feelings he had felt when he woke up.