MINES OF HAVEN AND GUYOT HILLS. 
339 
sheeted zone to the north. The ore minerals (probably svlvanite and calaverite, 
though these are not usually visible) occur in minute veinlets and in little vugs, 
containing quartz, fluorite, roscoelite, and pyrite, at the intersections of minute 
irregular fractures in the phonolite, which is itself impregnated with pyrite. 
The second “flat” ore body lies about 100 feet southeast of the Elkton shaft 
and is smaller than the one just described, extending eastward from the Walter 
lode for a distance of about 50 feet. It is a local expansion of the ore from the 
main lode along a set of probably not very persistent fissures which dip into the 
latter from the east at a low angle. The ore v r as associated with large open cavities 
lined with crystals of fluorite and quartz and containing loose masses of phonolite 
and breccia coated and in places partly cemented together by the same minerals. 
When first opened these cavities were found to be full of water, which is said to 
have flowed out in such volume as to flood the level in about an hour. It is not 
clear whether there was originally a small intrusive mass of phonolite at this point, 
but a portion of the country rock is certainly breccia. There appears to have been 
considerable local shattering, with probably a removal of some of the finer shat¬ 
tered material in solution by the abundant water which deposited the quartz and 
fluorite in the cavities so formed. As all of the ore had been removed at the time 
of visit, the details of its occurrence could not be studied. 
CHARACTER OF ORE. 
The ores of the Elkton mine occur in granite, monchiquite (“basalt”), breccia, 
and phonolite, and consequently exhibit considerable variety. The granitic ore is 
of the same general character as that described in the Ajax and Portland mines, 
but exhibits, if anything, more intense alteration. Much of this ore is exceedingly 
porous, even the original microcline phenocrysts being reduced to spongy skeletons. 
A part of the rock has certainly been removed in solution, while the remainder 
has in some places entirely recrystallized as a carious aggregate of adularia, quartz, 
fluorite, pyrite, and some calaverite, though the last is rarely visible. 
Under the microscope it is seen that the clear secondary feldspar is in many 
cases optically continuous with residual kernels of the older turbid microcline. 
Fluorite occurs partly in solid aggregates, but very largely as minute crystals 
disseminated through the partly sericitized microcline. Pyrite in aggregates or in 
small octahedral crystals occurs abundantly in both the original and secondary 
feldspars, showing a noticeable tendency in the older feldspar to develop in the 
vicinity of microscopic fissures. The exceedingly irregular pores or vugs of this 
ore are lined sometimes with quartz, sometimes with adularia, sometimes with 
fluorite, but more commonly with all three minerals, together with pyrite. Some 
of the pyrite as seen under the microscope is intimately associated with small 
quantities of an obscure opaque material, gray in incident light, which is probably 
molybdenite. 
Fluorite varies greatly in abundance in different parts of the ore bodies and 
is in some places absent. The average tenor of the granitic ore is about an ounce 
in gold to the ton. 
