primarily denoted anything transparent, e.g., a transparent stone or gem, hence, "a lens of crystal, a glass," Revelation 21:18,21 .
"a mirror," is rendered "glass" in the AV of 1 Corinthians 13:12; James 1:23 . See MIRROR.
Note: For the corresponding verb katoptrizo in 2 Corinthians 3:18 (Middle Voice), see BEHOLD , No. 12.signifies "glassy, made of glass" (akin to A, No. 1), Revelation 4:6; 15:2 (twice), RV, "glassy."