Currently based in Fort Lauderdale, Florida, Judson Mark Grosvenor maintains a strong presence in the San Diego entrepreneurial sphere and has served as the CEO of several San Diego businesses, including Teton Design, Jaymark Financial, and Grosvenor Industries. In addition to his executive responsibilities, J. Mark Grosvenor has an interest in gemology.

The field of gemology is a subset of geology and earth sciences. Essentially, it deals with identifying and working with jewels. A layperson may not be able to tell the difference between cheap cubic zirconia and expensive diamonds; gemologists, however, will be familiar with the distinctive qualities of a gemstone, such as color, clarity, and cut, to be able to differentiate between them. They also study other attributes of minerals to recognize different gemstones, such as refractive indexes or inclusions, which are materials trapped inside a gemstone during its formation.

Since jewelry and gemstones often serve as an investment, gemology is a necessary field for professional appraisers of these items. Many are licensed to certify the authenticity and quality of jewels. Jewelers in retail must also have an understanding of gemology to answer client queries and to identify gemstones that customers bring to them.