Lapis lazuli is a gem known for its deep blue color, which can range from azure to royal blue to indigo. The most demanded lapis lazuli is a dark blue with flecks of gold. It has a moderate hardness of 5 to 5.5 on the Mohs scale of hardness, which means it can be scratched by harder minerals like quartz and topaz, but can scratch softer minerals like gypsum and talc.