Obsidian and pumice are both volcanic glasses, but they are formed in different ways and have different properties.

Obsidian is formed when magma cools very quickly, so that crystals do not have time to grow. This results in a glassy, ​​black rock that is often used in jewelry and tools. Obsidian is typically a dark color, such as black or brown, and it has a conchoidal fracture, meaning that it breaks into smooth, curved surfaces.

Pumice is formed when gas bubbles are trapped in magma as it cools. These bubbles expand and cause the magma to become frothy and light. Pumice is a light-colored rock, often white or gray, and it has a vesicular texture, meaning that it is full of small holes. Pumice is used in a variety of applications, such as insulation, abrasives, and building materials.

Here is a table summarizing the key differences between obsidian and pumice:

| Feature | Obsidian | Pumice |

|---|---|---|

| Composition | Volcanic glass | Volcanic glass |

| Color | Dark (black or brown) | Light (white or gray) |

| Texture | Glassy | Vesicular |

| Formation | Cools very quickly | Gas bubbles trapped in magma |

| Uses | Jewelry, tools | Insulation, abrasives, building materials |