Gemologist Peters says there are no diamond mines in the USA. Yes and no. There are no commercially productive diamond mines, but there is the Crater of Diamonds State Park in Arkansas. Tourists can buy tickets to access a diamond field where they can dig for low grade diamonds.
Episode title: A Murder Is Forever. In 1947 the De Beer's Consolidated Mines started the single most famous and effective ad campaigne of all time with the slogan "A Diamond Is Forever".