Webster's 1828 Dictionary
MESOTYPE
n.[Gr. middle, and form, type. ] Prismatic zeolite; a mineral divided into three subspecies, fibrous zeolite, natrolite, and mealy zeolite. This is said by some writers to be so named from its property, when transparent, of doubling images. Others say it is a mean form between stilbite and analcime.
Webster's 1913 Dictionary
MESOTYPE
Mes "o *type, n. Etym: [Meso- + -type: cf. F. mésotype.] (Min. )
Defn: An old term covering natrolite or soda mesolite, scolecite or lime mesotype, and mesolite or lime-soda mesotype.
The Wordsmith Dictionary