Final answer:
Obsidian is the igneous rock that forms when magma cools so quickly that crystals do not have time to form, leading to the creation of a glassy, naturally occurring rock.
Step-by-step explanation:
The type of igneous rock that results when magma cools so quickly that crystals do not have time to form is known as obsidian. Obsidian is a glassy-textured, extrusive igneous rock, which forms very rapidly from the cooling of lava. This rapid cooling process prevents the formation of crystals, resulting in a natural glass that lacks minerals and is generally black in color. Because of its unique formation process, obsidian is an uncommon rock, yet it can be found at several famous localities such as the Yellowstone Caldera in Wyoming and the Newberry Volcano Caldera in Oregon.