of
albite and muscovite. A similar pocket from the Caterina mine at Pala,
shows only spodumene, pink clay, and quartz. The exhibit also includes
a pocket containing an abundance of small blue tourmalines; a small
pocket from the Tourmaline King mine, very rich in gem tourmalines; and
several pockets free from any gem stones. Such pockets are known by the
miners as " dead ones."
On
this same sloping shelf are shown also several large specimens of the
minerals associated with the gem pockets. Among these minerals may be
noted a fine example of orbicular muscovite, an altered perthite
(felspar) crystal, a large amblygonite crystal, and several speciments
of spodumene (kunzite) in the matrix. These kunzite specimens are very
difficult to collect, as in general the matrix of the kunzite is so
friable that it breaks to pieces when it is taken out of the mine.
The
three horizontal shelves above the sloping shelf on the north side of
the case contain well-developed and well-crystallized specimens of the
different minerals found in the gem-pocket zone of the pegmatite dikes.
Among these minerals may be noted in particular a good series of the
various forms of lepidolite (including several well-crystallized
specimens), crystals of muscovite, fine tourmaline crystals, albite and
orthoclase in well-developed crystals, pink beryl, stilbite,
cassiterite, a large crystal of lithiophilite, bismuth, bis-muthite,
bismuthosphaerite, purpurite, hematite and pyrite, apatite, pucherite,
topaz, manganotantalite, a fine example of clear pink kunzite in the
matrix, and the phosphate minerals first found in this locality,
namely, palaite, salmonsite, and sicklerite.
SELECTED BIBLIOGRAPHY FOR 1916.
Draper, David, and Goodchild, W.
H., Notes on the genesis of the diamond: Min. Jour. (London), May 20,
p. 357, May 27, p. 365, 1916. Among the conclusions stated are that
differentiation of the magma in the vent (kim-berlite pipe) toward the
end of the active volcanicity is formed by the sinking (gravitative
differentiation) of the early formed crystals (chiefly olivine and
iron-calcium pyroxenes). After the magma in the upper part of the vent
has solidified, the still molten part beneath Is continuously and
slowly impregnated with magmatic gases, chiefly water and carbon
dioxide, which delay the solidification of the mass and produce
extensive serpen-tinization (which is therefore not a weathering
result). During this process diamonds of commercial size are formed by
a process of secondary enrichment, large crystals growing at the
expense of the originally disseminated minute crystals.
Gottschalk, A.
L. M. The discovery of " kimberlite" in Brazil: Min. and Eng. World,
Dec. 16, 1916; also in Eng. and Min. Jour., vol. 102, Dec. 9, 1916. The
discovery of at least five pipes of kimberlite in Brazil is reported.
Gregory, H.
E. Garnet deposits on the Navajo Reservation, Arizona and Utah: Econ.
Geology, vol. 11, p. 223, 1916. The source of the garnets now found in
drift deposits is referred to the boulders and pebbles of garnetiferous
gneiss and schist of unknown formation brought up as inclusions from
unknown depths by dikes, now very much altered.
Kunz, G.
P. The production of precious stones for the year 1915: Mineral
Industry, vol. 24, pp. 591-613, 1916. Short notes of domestic gem
minerals include notes on diamond in Arkansas, labradorite in Utah,
opal in Nevada, and corundum in Montana.
Lacroix, Alfred, Sur
le mineral colorant le plasma de Madagascar et sur la celadonite: Soc.
franc, mineralogie Bull., vol. 39, pp. 90-95, 1916. The green color of
plasma is due to celadonite, a green silicate of iron, which probably
represents a group of mineral species of closely related composition
rather than a single definite species.
