Rubies are arguably the most precious and valuable of all colored gemstones. Rubies have been important in many cultures for thousands of years. Ruby is characterized by its vibrant shades of red, excellent luster (facets reflect light almost like a mirror), and hardness (it is difficult to scratch and therefore resilient). Ruby is named after the Latin word "ruber" for red. Ruby is the birthstone for those who are born in July. Ruby is also used to celebrate a couple's 15th and 40th anniversary.