Ruby

In modern times, Ruby is said to be a source of strength and protection.  It ignites one's zeal for life and invites one to follow their passions. It is great for boosting energy levels and igniting one's creative flare.  This gem promotes a clear mind, increased concentration and motivation, and brings one a sense of power, self-confidence and determination helping to drive one towards achievement and success.  It helps one face old fears and infuses us with the courage and tenacity to move forward despite hardships or misfortune. It emboldens, but also supports it's holder through defeat, tempering negative mindsets and anxiety that could otherwise consume them.  This crystal can also help one release caustic emotional influences, and is exceptional at helping one develop a more loving attitude toward one's self and one's body.  It helps one overcome old emotional wounds, helping to rebuild trust, especially when it comes to love and loss. This stone has always been a symbol of love and promotes faithful, passionate, committed, and intimate love.  It also reaches deeper, reinforcing and boosting compassion and perseverance.  It induces desire and acts as an aphrodisiac, and for this reason can be helpful in restoring and maintaining passion.  It's an excellent tool for grounding, helping it's holder feel safe, stable, and immutable to the forces of change.  For those looking to increase their status or wealth, this gem can be a major asset to them.  Ruby is connected to good fortune and leadership, and can help ease one out of their comfort zone and routines, allowing one to engage more fully in this area.  This stone does not spur one into rash or risky maneuvers, but rather helps guide our choices, putting one in the position of pursuing and attaining more.  Physically, this crystal 'strengthens' the heart, improves circulation, helps to detoxify the body, and is helpful in treating kidneys, lymph and adrenal glands.  It's considered very beneficial for reproductive systems and organs, and helps regulate cycles and functions as well as treating dysfunctions and imbalances.  It can support one in weight regulation, especially when it's rooted in emotional eating, and it can help with fever and infections. 

When speaking of stones, there are semi-precious gems, and then there are precious gems, and Ruby is 1 of 4 precious gems, the other 3 being emerald, sapphire and diamond.  It has a hardness of 9 on the Mohs scale, and is part of the hexagonal crystal system.  It's name is derived from the latin word for red and it's primarily found in Burma, India, Brazil, Thailand, Sri Lanka, and USA.  Natural rubies are imperfect and have rutile needle inclusions beneath their surface known as 'silk'.  This is one way to discern synthetic rubies from natural ones, and also increases the value of the stone.  When a Ruby is cut, the way the light and inclusions interact can cause a 'cat's eye' effect or in some cases may display a star.  Both natural and synthetic rubies are used commercially in watchmaking, for medical instruments, and for lasers for microscopic surgery. 
In folk lore, this crystal has always been thought of as powerful and valuable.  Some say ruby was the third eye of dragons.  They were believed to surpass all other precious stones in virtue, their value exceeding that of the diamond.  It symbolizes the sun, and its fiery complexion hints at a flame within the stone which legends claim could not be concealed by even the thickest of clothes.  The Chinese Emperor Kublai Khan was said to have offered a city in exchange for a sizable Ruby.  It was popular on crowns and other items worn by royalty because it was thought that the ruby made the king invincible and healed battle wounds.  Various other legends claim it could resist the effects of poison or allow one to live peacefully amidst enemies.  Burmese legend believed that sewing this stone beneath the skin could make one immortal.  It was worn as an amulet or charm to ward off plague and pestilence, warned its wearer of impending danger, kept the body safe, and banished sadness and foolish thoughts. It was reputed to bring its owner peace, drive away frightful dreams, restrain lust, and to help resolve disputes.  During the Middle Ages in Europe, Rubies were used to convey good health and remove negative energies from the user.