Which material is a type of lunar rock that has a crystalline structure?

Anorthosite is a type of lunar rock that is primarily composed of plagioclase feldspar, which gives it a crystalline structure. This rock is significant in the study of the Moon's surface and composition because it forms the bulk of the lunar highlands, showcasing the geological processes that shaped the Moon. The crystalline structure of anorthosite allows it to manifest the characteristics of igneous rocks, which cool from molten material and solidify into a structured form.

In contrast, while feldspar itself is a mineral primarily found in anorthosite, it does not specifically refer to a type of rock but rather to a component found in various igneous rocks. Natural glass lacks a crystalline structure because it is formed from rapidly cooled lava or volcanic material that doesn't crystallize during solidification. Pumice is also a volcanic rock but is characterized by its porous texture and is typically formed from frothy lava that cools quickly, leading to a glassy surface rather than a crystalline one.