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                                                    Cornwall Mine Area

                                          Cornwall, PA


November 3, 2012 (Saturday): Cornwall Tailings, Cornwall, PA (10:00 AM - 3:00 PM) Directions will be e-mailed to those who signed up.

We will be visiting a different tailings site than the golf course's this time. Tom Pankratz will update us just before the trip.

Site Geology

The minerals at Cornwall are associated with two major rock types:  diabase and limestone.  The Triassic diabase is an igneous rock of dark green to black color containing feldspars and pyroxenes, with minor amounts of biotite, ilemenite and hornblende.  The diabase formed by crystallization of these minerals from a molten rock that cut upward through surrounding cambrian and Ordovician limestone.  This diabase, as it cooled and solidified, recrystallized some of the limestone into marble.  Several minerals, such as diopside, actinolite, epidote, and garnet, also formed in the limestone partly as a result of the heat from the diabase and partly as a result of the addition of some chemical elements from the final crystallization of the diabase.  Later, additional solutions spread outward along the top of the diabase into the limestone.  The magnetite, hematite, pyrite, chalcopyrite, actinolite and chlorite formed at this stage.    Sometimes they replaced the limestone, and sometimes they replaced the previously formed diopside and actinolite.  The zeolites, sulfated, hydroxides, and copper carbonates crystallized last, filling open fractures and cavities.  The consequence of this series of geologic events has resulted in certain minerals occurring together.  Three such examples are the associations 1)  magnetite-chalcopyrite-actionlite, 2) zeolites-chlorite-magnetite, and 3) garnet-tremolite-calcite-serpentine.  The age of the ore deposit is approximately 190 mya, which is within the Triassic period.     Geologic Time Scale

MinDat list 75 minerals that have been found at this site.


The mines at Cornwall have been closed for some time, and are now imploded and/or flooded.  However extensive tailing piles remain and we have been granted permission to collect at one.  I don’t think we, or anyone else, has collected at this particular site.  It is quite large being perhaps 100 X 300 yds roughly a triangular shape.  The rocks appear to be mostly diabase; little limestone was evident.  Virtually all of the rocks are dinner plate sized and smaller.

Just to be clear, this site in NOT located on Haines & Kibblehouse quarries property. We will NOT be visiting their site on this fieldtrip. We have exclusive, express one-time permission from the landowners of the site that we will be collecting from this fieldtrip.

There are 2 other large tailings sites in the Cornwall area and I’m working on getting permission to visit them also.  One is diabase and the other limestone

NOTE:  It is about a mile walk from a parking area to the tailings piles.  For the most part it’s a very easy walk.  This is not necessarily a strenuous collecting trip, depending on how much you collect.


You will need to bring leather boots (I don’t think you need steel-toed), gloves and goggles (hard hat optional)  Bring rock hammers, chisels and small sledges (2-5 lb range), wrapping material and flats (I don’t think a sledge is necessary).  Also bring lunch, snacks and drinks if you want.


The site is in Cornwall, Pa which is a 1 - 2 hr. (60 mi.) drive from Delaware.   I will provide explicit directions to participating club members.

This Field Collecting Trip is for Delaware Mineralogical
Society members only

[Tom Pankratz, Vice-President of Fieldtrips]

Previous dates for this Fieldtrip:

May 12, 2012, Saturday: Cornwall Tailings, Cornwall, PA (10AM-3PM)

May 17, 2008, Saturday:  Haines & Kibblehouse Cornwall Materials Quarry, Cornwall, Lebanon County, PA: (8AM-12PM) (Tentative) This quarry produces magnetite, garnet, hematite, chrysocolla, pyrite, chalcopyrite and many other minerals.  Please sign up by May 15th if you would like to attend!

October 22, 2005, Saturday: Cornwall Mine, Cornwall, PA
DMS invites its members to visit the historic Cornwall Iron
Furnace in Lebanon County.  Combine a little bit of
history with some mineral collecting!  Junior members are
invited to attend!  The minerals that can commonly be found
here include: azurite and malachite coatings, calcite,
magnetite and pyrite. 
See for a list and
photographs of the minerals that have been found at this mine. 
For more information about the historic Cornwall Iron Furnace
and a location map, please see the following



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This page last updated:  January 17, 2013 09:16:39 PM

Next Meeting

January Program, Monday, January 13, 2014:

"DVD Presentation, Election"

General Club Meeting:
January 13, 2014

We are meeting at
The Historic Greenbank Mill,  Wilmington, DE

Special Meetings:

*Show Committee Meeting, January 9, 2014

*New Home/Lapidary Committee, 2014

*Board Meeting, to be determined

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