From Ohio Department of Natural Resources Newsletter 1984

Sunbury erratic east of Sunbury, Delaware County. This granite boulder is thought to be the largest crystalline erratic in Ohio.
What Is the Biggest Rock in Ohio?
Without question the honor of the largest glacial erratic, in the broad sense of the definition, goes to the famous Brassfield erratic near Oregonia in Warren County. This erratic was described in detail by J. J. Wolford in 1932. The Brassfield erratic was named because of its composition-Brassfield Limestone, of early Silurian age (about 430 million years ago). This massive chunk of limestone ranges in thickness from about 5 to 17 feet and covers an area of about an acre along the north fork of Olive Branch, a tributary of the Little Miami River, about 1/2 mile southeast of Oregonia, Washington Township, Warren County.

Wolford noted that the Brassfield erratic rests on glacial till of lllinoian age and is about 125 feet lower than the projected elevation of the Brassfield Limestone. This huge mass of limestone was transported by Wisconsinan-age glacial ice at least 4.5 miles and possibly farther. A small limestone quarry, known as the Betty Heidy quarry, utilized the limestone from this erratic at about the turn of the century.

No one questions the position of the Brassfield erratic as the largest in the state, but somehow this huge chunk of native limestone fails to capture the same sort of exotic spirit as the igneous or metamorphic erratics that were transported hundreds of miles and are very unlike any native Ohio rock. With this qualifier added to the original question-what is the largest rock in Ohio-the contest becomes somewhat more narrow.

The state champion erratic of igneous or metamorphic origin may have been the one reported by M. C. Read in his 1878 report of the Second Geological Survey of Ohio. Read reported that this granite boulder, located in the village of Ashland in Ashland County, had original dimensions of 25x15x12 feet with an estimated weight of 350 tons; however, he also stated that the boulder had occasionally been quarried for foundation stone over a period of 30 or 40 years prior to 1878, The dimensions of the boulder could not be verified by Read, so the reported size must be regarded with some caution because such figures are commonly exaggerated by local residents. A recent check with the Ashland newspaper and local historians was unsuccessful in confirming that any of the original erratic remains in this community today.

The state championship of crystalline erratics, both because of size and verifiable existence, must pass to the Sunbury erratic, located near the community of Sunbury in Delaware County. This large, oval-shaped granite boulder is 22 feet long, 18 feet wide, and 8 feet high and has a circumference of 72 feet. The weight of the exposed portion of the erratic is about 200 tons. The portion of the boulder below ground level is unknown. The Sunbury erratic is located 1 mile east of Sunbury on the north side of Croton Road and approximately 1/10 mile north of this road.

Today, Ohio's premier erratic lies in obscurity, surrounded by high weeds at the northwest corner of a beech-maple woodlot. During the 1930's, however, this erratic was relatively well known and was even marked as a point of interest on road maps of that era. According to Robert Skeens, a nearby resident with a lifelong interest in this boulder, a tombstone company once expressed interest in the Sunbury erratic but apparently decided that it would be too expensive to remove. So it now marks its own last resting place instead of contributing that function to a lot of people who probably never heard of glaciers in Ohio and always thought the term erratic referred to behavior."

                          The remainder of the article addresses other erratics in Ohio.


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