琉
リュウ, ル

precious stone, gem, lapis lazuli

JLPT1 G13 S0 F2036

As per 㐬# as described in 流 (flow) + 玉 jewel → *jewel* with a slippery surface over which the fingers flow. The compound 琉璃 is an abbreviation of 吠吠瑠璃, a transliteration of the Sanskrit vaidurya (lapis lazuli).

[Full Kanji Etymology List]