Many attribute the Peridot coming from an island off the southeast coast of Egypt in the Red Sea and the word derives from the Arabic "Faridat," the Arabic word for gem and the "t" is pronounced. This is how my jeweler in the jewelry district in NYC pronounces it and since it's my birthstone, I do too. But, both are correct in the dictionary. (Personally, I think it's just easier to order the diamond stuff instead-much less confusion!)