This is a rock called chert. Chert is sedimentary and is composed mostly of microcrystalline silica that are the shells of diatoms millions of years after they died and collected along the bottom of the Atlantic Ocean. Over time they compress, harden, absorb impurities like iron, and often form rock crystal formations and other formations such as these green nodules. In regular light, ie sunlight, room light and other visible light sources the small nodules are greenish in color, while the base rock, the chert, is a pale gray color. Under SW UV light, they floresce a bright green.