According to this site and Bowlingballreviews.com, it's a reactive pearl.
However, according to the eBay seller, it's EGT Particle. Here's a copy-and-paste from the auction along with the promise that this ball works in "the heaviest oil" (I knew that wasn't going to be right given its age and advancements in oil tech):
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"A completely redesigned weight block features an inverted tri-stack design with 4†flip blocks on top and bottom for tremendous flare potential (7†plus), surrounding the weight block is a light density 7 ½†core lowering the RG (2.47) and increasing the rev rate, providing you increased read in the mid-lane and dynamic backend power. Encompassing this core is a new EGT™ (Enhanced Gripping Technology) particle coverstock for increased traction in the heaviest oil."
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Jess