Ask-a-Geologist Video #11: Why do pumice and scoria have holes and granite does not?

Hi everyone, today we have another great ask-a-geologist question from one of our fabulous readers. Peter wrote to us and asked: Granite, pumice, and scoria are igneous rocks, but why doesn’t granite have airholes, but the other two do?

Ask-A-Geologist #7: Are amethysts a part of geodes or are the minerals in geodes different?

David asked: Are amethysts part of geodes or are the minerals in geodes different? Hi David, geodes can contain amethyst crystals. These unique samples form in open holes in sedimentary rocks such as limestone or igneous rocks likes basalt.