The Rebersburg Fulgurite

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The Rebersburg Fulgurite was discovered in Rebersburg, Miles Township, Centre County, Pennsylvania in November 2015 by Amish farmer, Samuel Weaver. Out of respect for the Amish and his privacy we are not using his real name. I visited Mr. Weaver at his home on March 16, 2022. According to Samuel, he was hunting deer in mid-November 2015 on private land near Rebersburg, PA. There was about an inch of fresh sleet and snow covering the ground and he was walking on a path through the woods. He came upon what he described as looking like the site of a large hot fire that had exploded. “I recall it so vividly,” he said. “There were dozens of pieces of something black scattered on the snow. I was confused because I knew something unusual happened, but I had no idea what it was. I stood there for 10 minutes or more. I remembered thinking ‘this is pretty, whatever it is’”. He then left the area to continue hunting.

The following year in the fall of 2016 he took his 11-year-old daughter and 7-year-old son on a hike to the same area. He came upon the site and found shards of black glass scattered among the fallen leaves. He also noticed a large chunk of what looked like molten glass protruding from the ground. His son asked if he could take a piece home. He gathered a few pieces and spent the next year trying to determine what it was.

In October of 2017, Samuel's friend contacted Lock Haven University. He and Samuel drove to meet with Associate Professor of Geology Dr. Loretta Dickson. They brought along a specimen of the glass for her to identify. At first, she too believed it was nothing more than slag, but she became interested after hearing the story behind the unusual piece. With her curiosity peaked, Dr. Dickson performed an XRF analysis on the specimen which concluded the material was similar to ordinary sandstone and did not contain any metals that would be present from furnace or glass slag. Could this be something more unusual than ordinary slag?

In late November 2017, Samuel and Schteff took Dr. Dickson and her colleague, Dr. Joseph Calabrese, to the location Samuel discovered over two years previously. It soon became apparent the mysterious black glass was not slag, but the result of a massive lightning strike. The heat of the strike instantaneously melted the native sandstone, turning it into molten glass. The resulting explosion created a blast zone almost twenty feet in diameter. Shards of obsidian like glass littered the ground. More importantly, the molten glass that Samuel found protruding from the ground was just the beginning of a large fulgurite buried slightly below the surface.

After photographing and mapping the fulgurite they began to carefully excavate the glass. This was no ordinary fulgurite. The lightning formed what can only be described as an obsidian tree, wide at the base, becoming narrower further along, with bifurcating branches extending almost ninety degrees from the main trunk. It measures approximately 16 feet in length, with at least four branches, each up to 4 feet long. The base of the fulgurite trunk is ten inches in diameter and comprised of a solid black glass core with a vesicular rim. As it disseminated through the sandstone and soil, the glass contained gas bubbles, or vesicles. The tubular branches became semi or totally hollow, with baked sandstone embedded on the surface. Finally, at the very end, the branches became pumiceous, so lightweight that its specific gravity is less than one, and the specimens float in water.

Specimens from the fulgurite range in size and composition from the site of the impact to the ends of the branches. The largest intact piece is solid glass, approximately eight inches in diameter, sixteen inches long and weighs nearly twenty-five pounds. Along with two other adjacent pieces, they form an impressive specimen nearly twenty-two inches long that weighs over forty-five pounds. Most pieces are between two to five inches, comprised mostly of vesiculated glass with embedded rock on the exterior. Some contain extremely rare iron silicide nodules up to 1cm in diameter. There are also exogenic glass specimens that exploded outward during the initial strike.  

The lightning strike, in a fraction of a second, appears to have produced what previously has occurred only in the extreme heat of an active volcano. It may well be the only fulgurite of its kind. This is the largest fulgurite ever discovered in Pennsylvania and it may well be one of the largest fulgurites in the world. Its historical value is without question.