Mesotype, or Natrolite

The peculiar colour of this variety of Zeolite caused it to be taken for a new species ; and its being' found by Klaproth to contain 10 per cent of Soda, that opinion was confirmed in the minds of several eminent mineralogists. Mr. Smithson having since found 17 of Soda in Mesotype, and the form of the spiculæ of Natrolite being the same as the crystals of Mesotype, there appear to be no longer any solid grounds for giving that mineral a higher rank in the system than that of an elegant and distinct variety.

Of the specimens figured one is from the British Museum, and another was presented to me by Prof. Strömeyer. They all come from Hohentweil in Swabia. It fills fissures in clink-stone porphyry. It is also said to occur in one or two of the western isles of Scotland.