. Ph ee ig cia laa 
448 EH. 8S. Dana—Association of crystals of Quartz and Calcite, 
Art. XLIX.—Mineralogical Notes. No. IV; by Epwarp 8. 
Dana, Ph.D.—On the association of crystals of Quartz and 
Caleite in parallel position, as observed on a specimen from the 
Yellowstone Park. 
THE occurrence of crystals of quartz in parallel position upon 
the faces of a rhombohedron of calcite was long since descri 
by Breithaupt. The relation of the two minerals is shown in 
gure 1, given by him; each crystal of quartz has its pyramidal 
A somewhat analogous case was 
described by Roset and Eck from 
Reichenstein in Silesia ; more recently vom Rath and Frenzel§ 
have given a full description, illustrated by a number of figures, 
of a similar occurrence from Schneeberg, Saxony. In the spect- 
mens described by them the calcite rhnombohedron (-} 2) was com- 
pletely enveloped by the quartz. Each rhombohedral face of 
the former having upon it a pyramid of quartz, united by @ 
yramidal face, and the extension of these six crystals regularly 
d produced a form which with its reentering angles appea 
to be a trilling (a compound crystal of three combined crystals) 
of quartz. It was further shown by vom Rath that the caleite 
alone had determined the position “of the quartz crystals, an 
consequently that the form, which had resulted, was only 4 
pseudo-trilling. Both the vertical twinning-plane, and the hori- 
zontal plane of the compound crystal were pronounced to 
te forms with quartz. oe 
any cases of the association of crystals of different species ® 
parallel position have been observed (as for example; of san 
on orthoclase, of pyroxene on hornblende, of chrysolite ‘ll 
humite, etc.), but the case here mentioned is of an exceptionaly, 
anomalous character. It is a matter of some interest, therefore, 
to note the discovery of a new case of this association of quartz 
and calcite and one which offers some features not — 
Dserved, affording at least a partial explanation of this geo™ 
nical relation between the two minerals. 
* Berg- u. Hiitten. Zeit., 1861, 54. H. Eck, ZS. G. Ges., xviii, £26 
+G. Rose, Pogg. Ann., Ixxxiii, 461. & Pose Ann., cly, 17, 1874. 
