This article's content is accurate to the most recent public game version, 0.4.8d.
"Crystallized psychic energy. Releases a mental blast to Confuse."
Mind Stones are consumable items that have a 50% chance of inflicting the 
Confused status effect on all enemies.
These items are incredibly rare as they only drop from a single enemy type that is limited in number. Due to their rarity, and the fact that there are skills capable of infliction confusion such as Alice's Mental Blast, it is best to save these as a last resort.
The following enemy drops Mind Stones:
- Mind Breaker (100% chance)