Gem Minerals in Museums 249
zona,
which, with subsequent additions from the same donor, is the most
striking feature of the whole collection; it is assembled and installed
in a single case at the north end of the small hall. After this
invaluable acquisition of the green and blue carbonates of copper from
Arizona, the Spang collection was purchased in the year 1891, which
doubled the number of specimens possessed by the museum, and added
many new varieties and kinds of minerals. In the nine years that
followed many valuable additions came from generous benefactors, and
in 1900 Mr. J. Pierpont Morgan purchased and presented to the museum
the remarkable collection assembled by Mr. Clarence S. Bement of
Philadelphia, characterised by the collector's superior scientific
judgment and exquisite taste —which evolved from the field of specimens
available throughout the world a great variety of forms representing
the commoner minerals— and the exceptional perfection of the specimens.
While the rock-bottom upon which modern mineralogy is founded is
chemical law, it might he said that crystallography is its foundation,
so that minerals of the same chemical type are grouped together, in the
modern scheme of exhibition ; and, under that type, minerals of
