April 28, 2012,
Saturday: Woods Chrome Mine,
Nottingham, PA (9AM+) Time changed! 1pm to 5pm
Geology and Minerals: The large variety of
minerals at the Wood Mine is the result of a complex geologic history.
Each of the different geologic processes crystallized a particular suite
of minerals, so that association becomes an important clue to the
minerals which one can expect to find. The first event was the
intrusion of a dark-colored rock (dunite) rich in olivine, and
containing lesser amounts of enstatite, chromite and magnetite.
The second major event was the introduction of hot solutions whose
composition was approximately that of serpentine. These solutions
also attacked the olivine-enstatite-chromite rock and formed new
minerals in addition to the serpentine (antigorite and chrysotile).
The new minerals thus formed were magnetite, uvarovite, Chrome-antigorite,
and chrome-chlorite (kammererite). Later, the composition of the
thermal solutions became such that chlorite-vermiculite, clinochlore,
and small amounts of pyrite were formed. Some magnesite and
brucite may also have formed along fractures in the rock. At this
time, there was no more chromium available to incorporate in definite
minerals, so that although these minerals are found in serpentinite,
they generally are not closely associated with chromite. Following
this later geologic event, weathering, ground waters, and relatively low
temperature solutions resulted in the deposition of magnesite,
hydromagnesite, calcite, chalcedony, aragonite, deweylite, cacoxenite,
genthite, brucite, and zaratite along fractures and in vugs within the
Safety and Liability: Steel-toed shoes, hard hat,
safety glasses and gloves are required. Wear clothing appropriate
for the season.
If the ground is too wet we’ll have to park most of our cars on the
driveway and take only a few 4-wheel drive vehicles to the
Directions: Directions will be provided to club members
participating in the field trip.
Gear: This is mainly a digging site. Bring pick, shovel,
hammers, chisels, prybar, brush clippers, small limb saw, hoe,
handtruck, boxes, wrapping. Mechanical excavation is no longer
allowed at this site.
DMS Contact: Tom Pankratz (cell 302 766
firstname.lastname@example.org) . I will be travelling Sept 3 –
18; during this time please contact me by email only.
[Tom Pankratz, Vice-President of Fieldtrips]