Shelby Gem Factory

The Shelby Gem Factory, also known as ICT Incorporated, was a Michigan company that manufactured artificial gemstones through proprietary processes. The factory made more varieties of man-made gemstones than any other in the world. It grew artificial gems and gem simulants, including synthetic ruby and sapphire and simulated diamonds, citrine, topaz, and other birthstone substitutes, and mounted them in gold or silver jewelry.
History.
ICT Incorporated, trade name "Shelby Gem Factory", is sited in Shelby, Oceana County, on the west coast of the Lower Peninsula of Michigan. It was founded in 1970 by Larry Paul Kelley. and Craig Hardy. Larry Paul Kelley and his wife Jo Kelly later retained full ownership making the Shelby Gem Factory a family business.
The Shelby Gem Factory initially produced only synthetic ruby, with ruby lasers being the principal application, to firms primarily in California. However, the greater profit potential of transmuting ruby rods into gemstones led to a change in the enterprise's focus. A colorless variant crystal was developed by experimentation with different materials and proportions. This was the first simulated diamond variety. It became the first business anywhere to mass-produce cubic zirconia (CZ). In the 1970s the Shelby Gem Factory rode a wave of popularity CZ then enjoyed. At its peak, tons of cubic zirconia were produced for the world market. Subsidiary factories were opened in China, India, and Panama to keep up with demand.
The factory closed in 2019, after 50 years of manufacturing. 
Factory.
Formerly, factory tours were offered. However, they were discontinued due to liability concerns attendant to the "very high temperatures and extremely bright light" and the unavailability of affordable insurance to cover the risk. Some of the furnaces burn at .
The factory features a museum, a showroom, and a theater and is a popular destination for schools, venture tours, and lapidary clubs. The 50-seat Art and Science theater shows visitors the differences between the processes that produce natural and man-made gems. Exhibits on-site include a lapidary machine visitors can try out for themselves to learn about gem cutting and a low-temperature model of a working crucible-furnace, along with photos of the now-off-limits factory floor.
The public can purchase gemstone jewelry from the factory. Jo Kelley, wife of Larry Paul Kelley, attributes the factory's increase in sales between 2008 and 2010 to the weak national economy.
Gem manufacturing.
The gems are synthesized in a furnace. It uses a US $85,000 heat resistant iridium crucible heated by surrounding electric coils. Temperatures range from . A crystal-producing mix is put into this furnace and melted. Then a slowly-spinning rod, the "seed", is lowered into the crucible, circulating the molten minerals, creating a homogeneous mixture and maintaining an even temperature throughout. Raised slowly over the course of weeks, the rotating rod cools the liquid and allows a large crystal to form. Kelley says it takes several weeks to grow a gem crystal.
The factory does not use the Verneuil method of "pulling" crystals, using temperature differences like the process that forms an icicle. Rather, it uses small fragments of mined gems, which are then used as seeds to re-crystallize liquid into larger gemstones. This is the so-called Czochralski process, which is akin to chemical vapor deposition. According to Kelly: "As far as I know, we are the only company on Earth that uses the second method."
Shelby Gem Factory workers then cut several dozen rough gems from each crystal using a diamond saw. A rough gemstone piece is placed onto a faceting machine, where over fifty facets are cut and polished to create a finished gemstone. ICT has a master jeweler on staff to mount the finished gemstones in gold settings; Kelley purchases rough gold castings from out of state, and finishes these at the factory to make settings as needed. The crystals made by the Shelby Gem Factory are used in jewelry and scientific industries worldwide. Unlike naturally-produced stones, these products are free of occlusions and internal and external flaws or inclusions.
The Shelby Gem Factory's simulated diamonds are diamond simulants, which are not to be confused with actual lab-grown synthetic diamonds. However, they can be difficult to distinguish from real diamonds. They have a Dcolor rating, the highest rating for diamonds (as determined by the Gemological Institute of America).
Although some of the company's products are "simulants" (such as their diamond simulants), their synthetic ruby and sapphire stones are not imitations – they have the same chemical and crystalline structure that is found in natural stones. The factory's FAQ says "our rubies and sapphires are really ruby and sapphire!"
The Shelby Gem Factory also manufactures simulated citrine and topaz, along with other birthstone substitutes.
As per the company website's FAQ section in 2017, below are the Mohs scale hardness values for some well-known gems along with Shelby gem products:
The company's policy is to maintain the confidentiality of celebrity clients, of whom there are many.