Hunt for RI’s rare state rock while hiking in Cumberland

Bring a magnet along to find a sample of the iron- and titanium-rich mineral named Cumberlandite, only found in abundance on four acres in this northern RI town.

CUMBERLAND — Two prominent families, the Blackalls and the Ballous, farmed, raised livestock, rode horses and lived for years on a rural stretch of woodland and low hills in the northern part of town.

Over the decades, urban sprawl, including apartments, houses, a commercial strip and a corporate park, crept toward the fields and forests.

But local conservationists managed to save 184 acres as the Blackall/Ballou Preserve. A natural oasis in the midst of development, the sanctuary offers family-friendly trails and reminders of the old farms, including miles of stone walls that separated pastures, wood lots and orchards. 

The preserve also has a unique feature — large piles of small rocks, including pieces of Cumberlandite, the official state rock of Rhode Island. It’s fun to try to find a specimen, but you need a magnet. (More on that later.)

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There are several entry points to the public preserve. I set out on a path at the southern end of the property, just off the parking lot for the Dollar Store on Mendon Road where the Benny’s used to be.

A blue birdhouse marks the start, followed by a set of 15 timber-lined stairs down to a series of wetlands. Depending on how much rain has recently fallen, the lowlands could be bone dry or swampy enough to attract bugs in warm weather. There are several wooden boardwalks and plank bridges that cross muddy areas covered with ferns and skunk cabbage.

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At an intersection, I went right on the wide, blue-blazed trail that stays mostly flat and meanders under oak and maple, with some beech, pine and birch trees. The trail then climbs a small hillside along some outcroppings, with private property on the right. I heard songbirds in the bushes and could smell honeysuckle.

After about a half mile, the path exits at another trailhead with signage on West Wrentham Road. The trail turns west, passes a few more birdhouses and continues under a powerline, with wildflowers growing on the cleared ground, before reentering the woods.

The path then comes to a junction. I turned right on a red-blazed connector trail that ran uphill for a short stretch before joining a yellow-blazed loop. I turned right, and soon noticed a white-blazed trail that runs east and may have been a horse path that leads to another trailhead on Old Wrentham Road, where the Blackall family had a farmhouse.

I stayed on the yellow-blazed trail and circled north until I reached the tip of the property, where I found a large, tall pile of stones that are too small to build walls but were probably cleared from the fields by farmers. I’d read that some of the stones are Cumberlandite, a rare iron- and titanium-rich mineral only found in large concentrations on four acres in Cumberland and in traces scattered throughout the Narragansett Bay watershed.

Cumberlandite, originally called rhodose, was formed 1.5 billion years ago when a small volcano melded 24 minerals and molten rock. The Nipmucks believed the rock was sacred, and early settlers mined it at a quarry just north of the preserve. At a nearby iron works, the ore was turned into farm tools, weapons, cannons and cannonballs during the Revolutionary War, but the casts were of poor quality and prone to cracking.

In 1966, the General Assembly declared Cumberlandite the official state rock.

Because of its high amounts of iron, Cumberlandite is slightly magnetic. I collected several charcoal-gray rocks with white flecks from the pile and passed a magnet over them. Eventually, one of the samples stuck to the magnet.


I pocketed the stone and continued on the yellow-blazed trail that turned south and crossed a narrow stream, one of three I passed that are easy to rock-hop over. On the right, beyond stone walls and through the trees, I could see many buildings.

The western half of the Blackall property was sold and developed as Highland Corporate Park for CVS and other companies. The eastern half was conserved as open space.

I followed the trail along a ridgeline downhill, back to the red-blazed connector trail that returned me to the blue-blazed loop. I went right and crossed a marked natural gas pipeline and the power line again and followed the trail on a slight jog west to another trailhead. The path then ducked back into the woods and along the banks of a small, quiet pond that may have been a watering hole for livestock. From there, I returned to where I started.

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In all, I walked 3.5 miles on the well-marked trails maintained by the Cumberland Land Trust, including 0.3 miles on the entry trail, 1.39 miles on the blue loop. 0.7 miles on the red connector and 1.15 miles on the yellow-blazed loop.

After the hike, I drove north on West Wrentham Road and took a left on Elder Ballou Meeting House Road to a historic cemetery. I walked about a hundred yards on a path behind the cemetery and found the abandoned quarry, with outcroppings of Cumberlandite.

It seemed a fitting end to a memorable morning hike, and I headed home with a souvenir in my pocket as a reminder.

Trail Tip

John Kostrzewa will discuss Walking Rhode Island and recommend easy and moderate trails during a presentation Aug. 3 at the Cranston Public Library. For details, go to

John Kostrzewa, a former assistant managing editor/business at The Providence Journal, welcomes email at

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