Rock glass

{
  "id": "MLC-T-IND-004895",
  "term": "Rock glass",
  "field": "Industrial and trades",
  "definition": "A naturally occurring volcanic glass formed as an extrusive igneous rock, created when felsic lava from a volcano cools rapidly with minimal crystal growth. Its composition is similar to rhyolite and granite, but its amorphous, glassy texture results from the rapid quenching process. This material, also known as obsidian, has a Mohs hardness of about 5 to 5.5 and fractures with a characteristic conchoidal pattern.",
  "subject": "Mining and extraction",
  "translations": {
    "de": "Gesteinsglas",
    "es": "vidrio de roca",
    "fr": "verre de roche"
  },
  "url": "https://mlchart.com/terminology/industrial/rock-glass/"
}