He
says "The results show a substantial agreement in the composition of
the mineral from the two localities, the most marked differences
apparently resulting from the substitution of magnesium and iron for
some of the manganese in the Greenland specimens. Sjöström represents
the composition of the mineral by the formula ROR2O.Ti02.4Si02 and the same form can be applied with equal degree of success to the new analysis."
NATROLITE.
Natrolite is the gangue in which the benitoite and nepttfnite occur, and it is also found in veinlets without associates.
Fracture
of the solid vein-stone shows a mass of xenomorphic crystals exhibiting
a good cleavage that yields more or less curved surfaces. The general
texture is granular but with common development of radiate forms quite
different from the usual radiate arrangement of natrolite and not
showing such distinct straight-line boundaries to the components.
Where open spaces occur in the veins allowing the formation of crystal faces, peculiar aggregates are found entirely unlike the
