Red corundum, also called ruby, is an aluminum oxide with a hardness of 9 on the Mohs scale. The durability of this gem makes it an ideal choice for rings and other jewelry that will see heavy use. Corundum is one of the most important gemstones in the world. It can be found in a variety of colors. Corundum occurs in nature in two primary crystalline forms: alpha corundum (or sapphire) and beta corundum (or ruby). The different forms have different properties: sapphires tend to be hard and transparent while rubies are softer and more translucent. Due to its simple chemical makeup, corundum has been produced synthetically since 1837, and gem-quality synthetic corundum entered the marketplace in the early 1900s. All colors can be produced synthetically, and huge sizes (more than 100 carats!) can also be achieved using Czochralski's Drawing Method. This process of growing corundum crystals involves taking the necessary oxide components for gem corundum (e.g., Al2O3, Fe2O3, TiO2, Cr2O3) in powdered form and melting them together in a hot content that is just barely over the crystallizing temperature. A rod with a small corundum seed crystal is lowered into the molten material and then very slowly removed. As the crystal is raised above the nutrient-rich molten mixture a small amount of corundum is formed at the interface between the seed crystal and the molten mixture. As the rod is slowly pulled upwards, new corundum continually grows below! Synthetic stone, as expected, is considerably cheaper than natural stone. NOT Dyed, NOT Composite Our stones are NOT dyed gemstones and NOT composite or assembled stones (Composite gemstones are cementing two or three pieces of stones together to produce a single one.) NOT Glass The chromium present in the stones causes a natural red fluorescence which is stimulated by both visible and invisible (ultraviolet) light. No Inclusions Our ruby stones are in VVS clarity, with no visible inclusions inside. They presents in pretty pigeon blood red under the sunlight. 250cts Raw Ruby Stone 350cts Raw Ruby Stone 600cts Raw Ruby Stone Add to Cart Add to Cart Buying Options Customer Reviews 4.5 out of 5 stars 33 4.5 out of 5 stars 33 5.0 out of 5 stars 3 Price $31.35$31.35 $45.75$45.75 — no data Stone Weight 250cts 350cts 600cts Gem Type Created Corundum Created Corundum Created Corundum Color Pigeon Blood Ruby Pigeon Blood Ruby Pigeon Blood Ruby Oval Loose Synthetic Ruby Round Loose Synthetic Ruby Oval Cabochons Loose Synthetic Ruby Octagon Loose Synthetic Ruby Teardrop Loose Synthetic Ruby Round Cabochons Loose Synthetic Ruby Add to Cart Add to Cart Add to Cart Add to Cart Add to Cart Buying Options Customer Reviews 4.6 out of 5 stars 34 4.5 out of 5 stars 37 4.1 out of 5 stars 12 4.7 out of 5 stars 39 4.6 out of 5 stars 15 3.0 out of 5 stars 1 Price $23.57$23.57 $15.22$15.22 $15.53$15.53 $23.61$23.61 $18.27$18.27 — no data Carats 2.5cts to 33.5cts 4cts to 22.5cts 4cts to 22.5cts 4cts to 18.5cts 2.6cts to 12.8cts 6.48cts to 24.21cts Stone Shape Oval Round Oval Cabochons, Flatback Octagon Pear Shape Round Cabochons, Flatback Color Blood Red Blood Red Blood Red Blood Red Blood Red Blood Red