All emeralds are usually treated to some degree. Oil is used to lubricate the gems in the cutting process. They are then usually dipped in oil again prior to selling. The key difference to note is whether the oil is clear or color-enhanced. Color-enhanced treatment lessens the stone’s value. An emerald with no enhancement is extremely rare and very expensive. If you are looking to spend a great deal and desire a stone with little enhancement or fill, it’s a good idea to ask for a lab verification certificate from the jewelers.
The ruby is the rarest and most expensive of the big three gemstones. Color is the most important aspect to choosing a quality ruby. You want to look for the deepest and most intense red you can afford. When it comes to tone, a medium to medium-dark tone is the goal.