Tan crystal kuma ana kiranta kristal shayi, kuma ma'adini na hayaki (ma'adini mai launin ruwan kasa) kuma ana kiransa hayaki crystal da tawada na rediyoactive Yawancin lu'ulu'u na shayi sune ginshiƙan hexagonal.Kamar sauran lu'ulu'u masu ma'ana, akwai wasu lokuta ma'anoni kamar tsattsauran kankara, gajimare da hazo.