Nijinite

Nijinite (Japanese: 虹ナイツ Nijinaitsu) is a fictional and fantastical mineral that come in the form of iridescent gemstones that serve as recurring objects in Britsune Garden.

They are said to be amongst the most precious and magical of stones found in the world.

Appearance
Nijinite stones come in different colours, and have an iridescence, hence its name.

Trivia

 * Niji (Kanji: 虹) means "rainbow" in Japanese, which refers to how it can come in different colours and have a multi-colour iridescence, whilst "-nite" is usually a suffix for a type of stone.