The Collaborative International Dictionary of English v.0.48:

Mesole \Mes"ole\, n. [Gr. me`sos middle.] (Min.)
   Same as Thomsonite.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Thomsonite \Thom"son*ite\, n. [From R. D. Thomson, of Glasgow.]
   (Min.)
   A zeolitic mineral, occurring generally in masses of a
   radiated structure. It is a hydrous silicate of aluminia,
   lime, and soda. Called also mesole, and comptonite.
   [1913 Webster]