The celtic knot is an ancient symbol of the journey of life. With no beginning and no end, the knot represents the timeless nature of our spirits and the world we live in. A Lab Ruby celtic knot combines these concepts with the spiritual attributes of the Lab Ruby . Gem of hot summer nights and steamy red sunsets, ruby is the birthstone of July. Show the world the passions within you with a fiery ruby ring. Sapphire is the birthstone of September, and one of the most popular gemstones on the jewelry scene today. The deep blue color of a sapphire ring is just right for an evening out.