Definition

Noun: * A type of natural, amorphous (non-crystalline) solid formed when molten lava or magma cools and solidifies too rapidly for mineral crystals to grow.

Usage

• "Volcanic glass" is an uncountable mass noun referring to the material itself. It is used to describe the substance that forms specific types of volcanic rock.
• The most common type of volcanic glass is obsidian.

Examples

• The sharp edges of the volcanic glass were used by ancient people to make tools and weapons.
• Under the microscope, the sample showed the characteristic conchoidal fracture and lack of crystals typical of volcanic glass.
• The rapid quenching of lava in water can produce volcanic glass.

Advanced Usage

• In geology, the term describes the texture and origin of a rock, not a specific mineral composition.
• It can be used attributively (like an adjective) to describe other features, e.g., "volcanic glass shards" or "volcanic glass fragments."

Variants and Related Words

• Obsidian (n): The most well-known variety of volcanic glass, usually black and glossy.
• Tachylite (n): A basaltic volcanic glass.
• Pitchstone (n): A volcanic glass with a resinous luster.
• Pumice (n): A light, frothy volcanic rock that can have a glassy texture but is full of gas bubbles.

Synonyms

• Natural glass
• Amorphous volcanic rock

Related Phrases/Compounds

• Volcanic glass shards: Small, sharp fragments of volcanic glass, often found in ash deposits.

Noun

1. a kind of natural glass produced when molten lava cools very rapidly