Silica may not be a word you commonly hear associated with diet (or foods that prevent hair loss, for that matter). If youâre looking to promote hair growth and prevent hair loss, however, silica will need to be on your menu.
keystone-the central building block at the top of an arch or vault. headstone, key. arch - (architecture) a masonry construction (usually curved) for spanning an opening and supporting the weight above it. building block-a block of material used in construction work.
From Diablo Wiki. Rift Keystones (or RKs) are small objects that drop randomly or are awarded for completing all five bounties in a given Act in Adventure Mode. RKs have no function on their own and are only useful to open up a Nephalem Rift.