CONTRIBUTIONS TO MINERALOGY FROM THE UNITED 
STATES GEOLOGICAL SURVEY. 
PREFATORY NOTE. 
By F. W. Clarke. 
Although mineralogical research occupies a relatively small place 
among the many varied activities of the United States Geological 
Survey, it is by no means neglected. From time to time interesting 
material is collected by the tield parties of the organization, and speci- 
mens deserving study are received from other sources. These are 
worked up, as opportunity offers, in the chemical laboratory of the 
Survey, sometimes independently and sometimes, as in the work 
reported in two of the memoirs here presented, in cooperation with 
the geologists by whom they were brought in. Occasionally assistance 
is received from investigators not connected with the Survey, and one 
such case is now represented by the joint paper of Doctor Hillebrand 
and Professor Penfield, of Yale University. In that instance the 
chemical work was done in Washington and the crystal lographic 
measurements were made at New Haven. 
Most of the papers contained in this bulletin represent investigations 
which are complete within themselves. The work done by Mr. 
Steiger upon the silver and thallium derivatives of the zeolites, how- 
ever, is to be regarded as one part of a series of researches upon the 
constitution of the silicates. Some parts of this series have been 
already published, and it is hoped that this work may be continued in 
the future. The field to be covered is enormous and progress within 
it is necessarily slow. Still, the results obtained so far are definite and 
significant, especially as the} 7 show a chemical plasticity among the 
silicates which was formerly unsuspected. 
Some of the items of more than ordinary interest to be found 
within these pages are as follows: Three new mineral species — moren- 
(Cite, coronadite, and plumbojarosite — are described. Natrojarosite, 
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