Some 3D printers use a sandstone/plaster as their printing medium in a technology called Selective Laser Sintering or "SLS". The license for this technology is held by ZCorp, the producers of the ZPrinter, but there are also open source models available online. SLS is also combined with inkjet technology to give 3D printed models full color capabilities. As of October 2013, this is the only viable solution to achieve a full spectrum of colors in 3D printing.
3D printing in plaster is used mainly for display purposes. Given the more brittle nature of the material, it does not lend itself to products with moving parts or that might be stressed by physical interaction.
For more information see our entries on “ZPrinter”, “Powder Bed Printing”, "Selective Laser Sintering" and “Inkjet Head Printing”.