MES'OTYPE, noun [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.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI