Spherulites in rhyolite   Spherulites are radiating masses of fibrous crystals in a glassy matrix. These spherulites are probably composed of alkali feldspars and some polymorph of SiO2, and in this cross-polarized shot, appear as round objects with dark crosses. Note the large phenocryst which forms the nucleus of one of the spherulites at center-left.		UNC sample WYO-14
		Rock type rhyolite
		Locality Wyoming