In November, the industry saw the debut of yet another lab-grown diamond company: Diamond Foundry. This one is noteworthy for being backed by Blood Diamond star Leonardo DiCaprio as well as a group of Silicon Valley billionaires including the founder of Twitter. Head of commercial relations Alon Ben-Shoshan discussed the company with JCK via email.    JCK: Unlike other lab-grown diamond companies, you are not offering diamonds, but diamond jewelry. How does that model work? Ben-Shoshan: When an order is placed on DiamondFoundry.com, we ship the diamond to the jewelry designer who crafts the final piece and ships it to the customer. The designer receives 100 percent of the revenue on their semi-mount (minus the same credit card fee that we pay). The relationship with the customer around the jewelry is managed by the designer. This model allows designers to treat our cus