Context: This is a piece of obsidian. Do you see the smooth, glassy surfaces of this rock?
Obsidian forms when melted rock cools very quickly. The rock is usually black, brown, or tan in color. Some pieces of obsidian contain swirls of two or more colors.
What type of rock is obsidian?
A. sedimentary
B. igneous
C. metamorphic
From the given choices, pick the correct answer and respond by indicating the letter of the correct option.

B