Answer:
The correct answer is glassy.
Step-by-step explanation:
Obsidian, or also known as volcanic glass, is a type of igneous rock (volcanic rock belonging to the silicates), formed by aluminum silicates and a large percentage of silicic oxides.
The obsidian is formed when a volcano emerges lava that cools quickly, which has a minimum growth of crystals. In the flows where it is obtained, the high silica oxide content induces a high viscosity and degree of polymerization of the lava. The inhibition of atomic diffusion in this highly viscous and polymerized lava explains the lack of crystal growth, giving shape to the glassy texture.
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