Forget plastic, glass, ceramic, and metal. Sand could become the most important 3-D printing material out there.

Thanks to sand casting, which accounts for over 70% of metal casting, 3-D printing companies capable of printing with sand have a tremendous opportunity to benefit. In the video below, Fool.com contributor Steve Heller details the process of sand casting and how 3-D printing companies like 3D Systems (NYSE:DDD), Stratasys (NASDAQ:SSYS), and ExOne (NASDAQ:XONE) could all stand to benefit.

Fool contributor Steve Heller owns shares of 3D Systems and ExOne. The Motley Fool recommends 3D Systems, ExOne, and Stratasys. The Motley Fool owns shares of 3D Systems, General Electric Company, and Stratasys and has the following options: short January 2014 $36 calls on 3D Systems and short January 2014 $20 puts on 3D Systems. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.