1897.] Mineralogy. 331° 
Unusually fine opals from near Salmon City, Idaho, as well as other 
occurrences of opal in Idaho, Washington, Oregon, Arizona, Califor- 
nia, Colorado and Georgia are mentioned. Australian opals were sold 
for more than $100,000 in 1896. 
In addition to the above named gems, mention is made at greater or 
less length of andalusite, cyanite, garnet, quartz, amethyst, chrysoprase, 
plasma, moss agate, labradorite, lapis lazuli, rhodochrosite, realgar, 
amber, xenotime and monazite. 
The total value of the gem production in the United States for 1895 
is placed at $113,621, of which $50,000 is accredited to turquoise. 
The Coloring Matter of Minerals.—The cause of the varied 
colors of certain minerals is discussed by Weinschenk,’ who presents a 
large number of facts tending to show that these colors are much less 
frequently due to organic substances than has been hitherto assumed. 
From considerations of the paragenesis of minerals, it is suggested that 
compounds of the elements tin, zirconium, titanium, cerium, didimium, 
lanthanum, nickel, tantalum and beryllium are in many cases more 
likely to be the true source of the minerals’ colors. The effect of the 
cathode rays and X-rays in producing a similar color in minerals, 
even in some cases where the color had been previously destroyed by 
heating, is cited as evidence against the organic nature of the coloring 
matter (?). The occurrence of colored minerals as a result of the cool- 
ing of a fused magma is evidence in the same direction. The sugges- 
tion is thrown out that the color of certain minerals may be a valua- 
ble index to the conditions of their origin, when investigation shall 
have determined the true cause of the color. 
Pearceite and Polybasite.—The systematic working out of the 
relationships existing between various isomorphous minerals has re- 
ceived another important contribution from Penfield. Hitherto the 
name polybasite has been applied to a group of minerals whose chem- 
ical composition is of the type seen in the formula Ag, SbS,, in which 
Ag is partly replaced by Cu, Fe or Zn, while the isomorphous arsenic 
molecules may occur in any proportion, almost to total replacement of 
antimony by arsenic in some specimens. The new name Pearceite is 
proposed in honor of Dr. Richard Pearce of Denver, Col., for the sul- 
pharsenite, while the old name polybasite is restricted in its application 
to the sulphantimonite. 
ê Zeitschr. d. D. geol. Ges., XLVIII, pp. 704-712, 1896. 
ê Am. Jour. Sci., CLII, pp. 17-29, July, 1896. 
