Collecting cumberlandite at Iron Mine Hill, RI

Cumberlandite, Rhode Island's state rock, is an intrusive igneous rock with phenocrysts of white plagioclase feldspar on the order of a centimeter in size set in a black groundmass of ilmenite, magnetite, and olivine (usually serpentinized). Cumberlandite has been used as an iron ore; it can be identified by its dark color and high density. Boulders of cumberlandite have been distributed across Rhode Island by glaciation. All these cumberlandite chunks come from one locality: Iron Mine Hill in Cumberland, RI. In this page I'll describe collecting cumberlandite at Iron Mine Hill. You can view high-resolution versions of all the images on this page by removing "-small" from their filenames.

Traveling to Iron Mine Hill: Iron Mine Hill is immediately west of the intersection of Elder Ballou Meeting House Road and West Wrentham Road, in Cumberland, RI, a little less than 15 miles north of Providence. I won't presume to give detailed driving directions, but taking State 114 north from Pawtucket will get you pretty close. State 114 also passes by Diamond Hill, a bluff of vein quartz, which I will describe in another page. I'm a graduate student, so I don't have a car: I biked up the Blackstone River Bikeway to Manville, rode up Cumberland Hill, and then headed north on West Wrentham road to Iron Mine Hill. This route is 17 miles one way, according to Google Maps, but it's not an easy ride: the surrounds of Iron Mine Hill are several hundred feet higher than the Blackstone River valley. Manville Hill Road through Cumberland Hill is particularly steep, although the neat exposures of shale along the roadside make this slog more tolerable.

Once you're at the intersection of Elder Ballou Meeting House Road and West Wrentham Road, head about a thousand feet west along Elder Ballou Meeting House Road to Ballou Cemetery. Here's a picture of Ballou Cemetery:

Ballou Cemetery from Elder Ballou Meeting House Road

I'll describe this historic cemetery in more detail at the end of this page. Head to the southern edge of the cemetery, far from the road. A trail leads past the cemetery's stone wall south-southeast to Iron Mine Hill. Here's part of the cemetery's stone wall near the trail:

Ballou Cemetery stone wall

Collecting cumberlandite at Iron Mine Hill: The northwest part of Iron Mine Hill rises 10-20 feet above the south part of the graveyard. Weathered gray cumberlandite outcrops along the side of the hill:

Iron Mine Hill cumberlandite outcrops

At the top of the hill is a level clearing:

Clearing atop Iron Mine Hill

Cumberlandite outcrops throughout the clearing. There is not much wildlife: I was bothered by flies in the forest at the base of Iron Mine Hill but they abandoned me as soon as I reached the clearing. The soil present is thin, rocky, and host only to ground cover. Trees grow in a raised area at the center of the clearing with thicker soil.

Iron Mine Hill's thin soil

This clearing is not a good place to collect cumberlandite: most of the cumberlandite exposed is oxidized.

Cumberlandite oxidizing atop Iron Mine Hill

Scattered across the clearing are iron objects, evidence of mining (as well as more quotidian trash):

Scattered across the clearing are iron objects, evidence of mining (as well as more quotidian trash):

An identified iron cube

The best place to collect cumberlandite is on the outcrops along the edge of the hill. Near the highest point of these outcrops are chunks of relatively unaltered cumberlandite that make good hand specimens. (I took two.)

Some good cumberlandite hand specimens

More evidence of mining is this drill hole into a cumberlandite boulder. There seems to be a wasps' nest in the drill hole:

A drill hole in a cumberlandite boulder

As it turns out, Iron Mine Hill is somewhat larger than these outcrops and this clearing. Here's a top-down view of the Iron Mine Hill area with my traverse of the hill outlined in blue (north is up; the intersection of Elder Ballou Meeting House Road and West Wrentham Road is at right):

A plan view of my traverse of Iron Mine Hill

Viewed obliquely, Iron Mine Hill can be seen to continue to rise to the right (towards private property on West Wrentham Road):

An oblique view of my traverse of Iron Mine Hill

I didn't realize the hill extended so far southeast and, upon seeing this map, worried that I had missed Iron Mine Hill entirely. However, in the pamphlet "Rhode Island Geology for the Non-Geologist" by Alonzo W. Quinn, which I purchased from the University of Rhode Island, Iron Mine Hill is described as approximately 1200 by 500 feet. The hill most prominent in the oblique image above is only half this size! What happened to Iron Mine Hill? Quinn writes "Half or more of the hill has been quarried for road metal." The clearing that I explored is the portion of Iron Mine Hill that has been mined away. The rise to the southeast is the unmined part of Iron Mine Hill. Below is a rectangle measuring approximately 1200 by 500 feet that shows the extent of the original hill.

Iron Mine Hill, unmined

Exploring Ballou Cemetery: Ballou Cemetery is an attractive, if somewhat run down, New England cemetery. Many of the gravestones are in poor repair.

A broken gravestone in Ballou Cemetery

This can hardly be helped by their cumberlandite construction.

A cumberlandite gravestone in Ballou Cemetery

Even some fenceposts are made of cumberlandite. These posts are badly weathered. Notice the Ballou name on the gravestone at left. The Ballou family must be important in Cumberland (Ballou Cemetery, Elder Ballou Meeting House Road).

Cumberlandite fenceposts in Ballou Cemetery

The more recent gravestones are sensibly made of granite. Here's a closeup of the Ballou gravestone from the previous image. Notice how fresh this granite (maybe Westerly granite?) looks.

A granite gravestone in Ballou Cemetery

Making rubbings of New England gravestones is a wholesome activity. Here's a rubbing I made of the 200-year-old cumberlandite gravestone pictured above:

A gravestone rubbing I made

I would like to return to this locality and explore the other half of Iron Mine Hill. To the best of my knowledge, specimens of cumberlandite have never been radiometrically dated: that would be interesting to do in the future. I extend an invitation to all readers of this page to visit Iron Mine Hill or other interesting Rhode Island localities with me. My email's on this site's main page. We could even bike to Iron Mine Hill together! Here's my bike in Ballou Cemetery:

My bike and my things in Ballou Cemetery