Ruby's day is Tuesday, its season summer, its apostle St. Matthew. The scarlet-colored gem, July's birthstone under the sign of Cancer, is said to accord wearers wisdom, happiness and health, and to bring particularly good luck to gamblers and lovers. Rubies are more than talismans or good-luck charms, not only historic and exotic but also valuable.
Great rubies display all three hallmarks.
The beauty of their color is without peer. And their durability is often a surprise to new buyers. On the famous Mohs hardness scale of 1 to 10, everyone knows that a diamond, as the hardest natural substance on earth, rates a 10. Rubies, at Mohs 9, are harder than any other material except diamonds. You may already have noticed that rubies and sapphires are often paired.