Yes, CONCRETIONS is a Scrabble word!

Letter values in Scrabble US: C 3, O 1, N 1, C 3, R 1, E 1, T 1, I 1, O 1, N 1, S 1.

Is it a valid word?

CONCRETIONS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

the formation of stonelike objects within a body organ (e.g., the kidneys)
a hard lump produced by the concretion of mineral salts; found in hollow organs or ducts of the body
an increase in the density of something
the union of diverse things into one body or form or group; the growing together of parts

Not playable in Scrabble US: COALESCENCY.