rock crystal
Mineralogy term for a transparent, colorless variety of quartz.
六方石は水晶の一種で、装飾品に使われることがある。
Rock crystal is a type of quartz and is sometimes used for ornaments.
The term 六方石 is composed of 六方 (ろっぽう, 'hexagonal') and 石 (せき, 'stone'), referring to the hexagonal crystal habit of quartz. The exact historical derivation is uncertain.