Parker shaft minerals

Overview

Among the hundreds of different mineral species found at Franklin-Sterling Hill, New Jersey, there are several subgroups that have a special significance to local mineral collectors. One of these is referred to as the Parker shaft minerals.

The term "Parker shaft minerals" lacks precision, but it generally refers to those minerals characteristic of the more unusual finds made during the short life (~15 years) of the Parker mine. All of these are secondary minerals, and a number contain water, suggesting low-temperature formation.

	Datolite (glassy clear) and roeblingite (white to cream). Franklin, NJ. Width 4 cm.

The Parker mine was the first to explore the deep, far northern limits of the Franklin orebody, and the Parker shaft provided access. Because of the peculiar minerals first found in areas mined through the Parker shaft, the name has become well known in mineral collecting circles, connoting the more rare and exotic of Franklin minerals.

	Parker mine buildings. Parker shaft headframe on the left-center; boiler buildings on the right. Looking north-northeast.

"Parker shaft" specimens often contain rare species, in complex associations, and sometimes fine euhedral microcrystals.

	Ganophyllite (brown) and prismatic willemite crystals (very pale green). Franklin, NJ. Width 4 cm.

Several of the more unusual species fluoresce, as do a great many of the associated minerals, making some specimens of "Parker shaft minerals" quite beautiful under ultraviolet light.

	Margarosanite and wollastonite, fluorescing blue-white and orange, respectively, under short-wave ultraviolet light. Franklin, NJ. Width 3 cm.

	Manganaxinite (red) clinohedrite (orange) and xonotlite (blue). Fluorescent response under short-wave ultraviolet light. Franklin, NJ. Width 3 cm.

	Hancockite (deep red-brown) and clinohedrite crystals (white), in a matrix of massive hancockite (brick-red), andradite (yellow) and franklinite (black). Franklin, NJ. Width 1.5 cm.

Such finds (collectively referred to here as the 'first find') included a number of new-to-the-science species recovered in small amounts in the late 1890s.

These minerals (and the year they were first described) are:

Later study of samples recovered from this time added margarosanite to the list of new-to-the-science minerals recovered through the Parker shaft. Glaucochroite and leucophoenicite were later found in various other occurrences in the Franklin mine as well.

	Nasonite (white to cream, center) and barysilite (pearly white plates), with manganaxinite (pale yellow), willemite (pale green) and andradite (yellow-brown). A classic "Parker shaft" specimen. Franklin, NJ. Width 5 cm.

The approximate location of this 'first find' underground is known. Much of the material was encountered during the driving of two raises upwards from the lower levels of the mine in 1895.

	Manganaxinite (pale yellow) and hancockite (brick-red), with hendricksite (black). These minerals are often major components of "Parker shaft" specimens. Franklin, NJ. Width 10 cm.

This area later became a part of the Palmer shaft pillar, a large section of the orebody overlying the Palmer shaft, that was left intact until late in the life of the Franklin mine. From approximately 1944-1954 mining operations once again worked this area, and many specimens of the unusual minerals the Parker shaft had encountered some fifty years before were recovered.

	Palmer Shaft pillar vertical section. Partial view of the keel area. Photo of an original hand-colored geological map of the famed Palmer Shaft pillar area.

	Hancockite (brick-red) andradite (brownish-yellow) and prehnite (white). Typical altered hancockite specimen with cellular patches of drusy crystals. Franklin, NJ. Width 10 cm.

	Hancockite (brick-red) andradite (yellow) and franklinite (black). Detail of cellular portion of specimen above. Franklin, NJ. Width 1 cm.

Most of this 'second find' of specimen material was recovered by observant miners, such as Nicholas Trofimuk of Franklin, and was ultimately deposited in the USNM and the Harvard Mineralogical Museum.

Later study of  "Parker shaft" specimens resulted in the discovery of the new minerals charlesite (1983), minehillite (1984) and franklinfurnaceite (1987).

Cahnite was found in small amounts in a variety of occurrences in the Franklin mine, including specimens of "Parker shaft minerals", and so may be found on lists of "Parker shaft minerals."

	Franklinfurnaceite. Twin crystals. From a vug also containing clinohedrite and hodgkinsonite crystals. SEM view. Franklin, NJ. Width 0.1 mm.

In addition to the new-to-the-science species noted above, a number of other unusual minerals are found in specimens from both finds. Also present are species more widely known but, as found in Franklin, are somewhat characteristic of these finds:

	Additional species characteristic of "Parker shaft" specimens
	Barysilite Kentrolite Cahnite A Lead Copper A Manganaxinite A Cuspidine Pectolite Datolite Pennantite-1a A Ganomalite Prehnite Ganophyllite Thomsonite Grossular A Vesuvianite A Hodgkinsonite A Xonotlite    A Also well known from other occurrences at Franklin.

	Kentrolite. Sheaves of deep red needles from a "Parker shaft" manganaxinite specimen. SEM view. Franklin, NJ. Width 0.4 mm.

	Native copper in willemite (pale green), with calcite (white) and franklinite (black). Though there are many occurrences of native copper in the Franklin mine, it is especially known from specimens of "Parker shaft minerals", and so appears on lists of "Parker shaft minerals." Franklin, NJ. Width 9 cm.

Species present in "Parker shaft" specimens that are truly widespread elsewhere in the mine (e.g. calcite, andradite, willemite, franklinite, hendricksite) are not included in the following list of "Parker shaft species". Secondary minerals which were found in the northern end of the Franklin mine, but not in direct association with the first or second find species, are not included either.

There are quite likely many different altered or recrystallized areas in the northern portion of the Franklin orebody, and not all are included in this author's interpretation of the term "Parker shaft minerals."

	A list of some "Parker shaft" minerals
	Barysilite Kentrolite Cahnite A F Lead Charlesite F Leucophoenicite A Clinohedrite F Manganaxinite A F Copper A Margarosanite F Cuspidine F Minehillite F Datolite Nasonite F Franklinfurnaceite Pectolite F Ganomalite Pennantite-1a A Ganophyllite Prehnite F Glaucochroite A Roeblingite F Grossular A Thomsonite F Hancockite Vesuvianite A Hodgkinsonite A F Xonotlite F  F Fluorescent in ultraviolet light.         A Also well known from other occurrences at Franklin.

Because the in-situ relations for these minerals are not well understood, today it is not certain if there was actually one, two or more occurrences of "Parker shaft minerals" in the northern part of the Franklin mine.

	Barysilite. Fine specimen showing masses of large, pearly plates. Franklin, NJ. Width 5 cm.

Also, the term "Parker shaft mineral" has engendered debate in the local collector community: any rock brought up through the Parker shaft could potentially (but trivially) be called a 'Parker shaft' mineral; and specimens not brought up through the Parker shaft, but of clearly allied occurrence, may quite sensibly be termed "Parker shaft minerals". The above list is merely this author's opinion on the matter.

	Willemite and hodgkinsonite crystals. Fine material for microscopic study. Crystals from a typical vuggy "Parker shaft" specimen. SEM view. Franklin, NJ. Width 0.5 mm.

In many cases these minerals have formed in various fractures, vugs and through replacement. A number are found in euhedral microcrystals, and hand-sized specimens may contain a very large number of species. The associations are complex and numerous.

Such "Parker shaft" specimens present fascinating subjects for microscopic study (see barysilite and ganomalite as an example). Today the study of these minerals is constrained to hand specimens, with the Franklin mine closed and flooded since 1954.

For further information on these minerals, see Dunn (1995).

	Nasonite crystals (green) embedded in clinohedrite (yellow). Thin-section viewed with crossed polarized light (false colors). Franklin, NJ. Width 1 mm.

	Ganomalite crystals (hexagonal outline) embedded in clinohedrite (yellow). Thin-section viewed with crossed polarized light (false colors). Franklin, NJ. Width 1 mm.
[to TOP of page]