256 R. Pumpelly—Paragenesis of Copper 
often impossible to distinguish as to the relative ages of the 
two. cimens in my collection offer conclusive proof 
that each of the following cases occur. 
. 
L—The copper was present before the calcite began to form, and 
became enclosed in the growing crystal. 
In this way calcite crystals, formed in a cavernous mass of 
copper, are intersected internally by a perfect net-work of thin 
plates of the metal, and yet preserve their cleavage unaffected ; 
but wherever the copper comes in contact with the surface of 
the crystal, the small entering faces are present. 
IL—The crystal of caleite was partly formed, then became incrus-— 
ted with copper, and was finished by a new growth of caleite over 
the metallic film. 
A most remarkable instance of this case is that of a crystal 
over the side-faces. All of these younger crystals are arraD 
of Sera uniformity with the plan of the underlying, older 
individual. 
Those portions of the surface on which the copper-coating § 
perfect have no younger calcite crystals; these occur where th 
metallic film is thinnest and more or less perforated. 
The copper is not confined absolutely to the surface of the 
crystal on which it lies; it penetrates to a slight distance along 
the cleavage-planes, and the result is an exceedingly delicate 
treiculation on its under surface. The calcites which at 
planted on the copper contain brilliant particles of the me tals . 
