Which geographical source is NOT known for producing sapphires?

California is not typically recognized as a significant source of sapphires. While some gemstones can be found in the region, including certain varieties like tourmaline, the production of sapphires is not a major aspect of California's gemstone output.

In contrast, Yogi Gulch, Madagascar, and Kashmir are all renowned for their sapphire deposits. Yogi Gulch, located in the United States, has gained attention for producing sapphire gemstones. Madagascar is particularly famous for its diverse assortment of sapphires, known for their vibrant colors and high quality. Kashmir is legendary for its deep blue sapphires, which are highly sought after due to their historical significance and unique color saturation.

Thus, California stands out as the least significant contributor to sapphire production among the mentioned sources.