The stone can absorb light to glow at dark repeatedly, safe, environmental and energy-saving to be as decoration of fish tank, garden, pool, etc. Features: It can luminous (dark place) in few minutes after normal absorption. The longer the absorption time, the longer the luminous time. Absorbs the light and after repeatedly luminous. Nice decoration for home, fish tank, garden, pool, etc. Safe, environmental and energy-saving. Specifications: Material: Bare stone Color: Blue, Green (optional) Item Size: 10-30mm / 0.39-1.18in Item Weight: 100g / 3.53ounces Package Size: 120 * 80 * 30mm / 4.72 * 3.15 * 1.18in Package List: 1 * Bag of Luminous Stone