On a technical level, a gemstone is a piece of valued mineral that’s chosen for jewelry. It’s a very broad category that includes common stones like amethyst and rare gems like padparadschas; soft minerals like opals and diamonds, the hardest material on Earth; and both organic gems and crystalline minerals. What gems share is their unique appearance that people treasure. They have special color, distinctive lustre, and scintillation that sets them apart from mere rocks or pebbles.

At Costello Jewelry Company, gemstones are our life. There are few pieces of bridal and designer jewelry we offer that don’t have one diamond or colored gemstone set in them, and there’s always a gemstone to fit a customer’s tastes.


The most treasured of gemstones, diamonds are a natural fit for any type of jewelry. They possess a special set of traits that turn light into rainbows of color, sparkle, and glow. This, paired with their natural durability and pure clarity, makes diamonds ideal for both center stones and accents for other gems.

Alongside diamonds are the “first-order gems,” which is the loose category for the most valuable gems. Blue sapphires, rubies, and emeralds fall into this category. Known for their extremely rich color and hardness, they provide an amazing complement to diamonds—and compete with them for a place of prominence in many pieces of jewelry.

Alternatively, if you’re searching for something with a bit more personality, you may appreciate birthstones. There are gems associated with every month, and if you want to purchase a piece of jewelry that will express your uniqueness or show a loved one that you know them on a personal level.

  • January: Garnet
  • February: Amethyst
  • March: Aquamarine
  • April: Diamond
  • May: Emerald
  • June: Pearl, Alexandrite, or Moonstone
  • July: Ruby
  • August: Peridot
  • September: Sapphire
  • October: Tourmaline and Opal
  • November: Topaz and Citrine
  • December: Blue Topaz and Tanzanite

And speaking of pearls, there are “organic” gemstones that are made by some living process: Pearls and mother of pearl come from oysters; spiny oyster makes multicolored jewels for pieces of fashion jewelry. And when you can find it in designer jewelry, amber also falls under the category of organic gemstones.

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