noun
pitchstone
A geological term for a type of volcanic glass with a resinous luster, similar to obsidian but containing more water. Used mainly in scientific contexts.
ピッチストーンは、黒曜石に似た天然ガラスの一種です。
Pitchstone is a type of natural glass similar to obsidian.
Obsidian is a more common volcanic glass with lower water content and a glassy luster, while pitchstone has a pitch-like resinous luster.
Borrowed from English 'pitchstone', a compound of 'pitch' (referring to its resinous luster) and 'stone'.