Dennis worked in diamond exploration both domestically and in the jungles of Indonesia in the early 1980s. He continued his interests in diamond exploration in 1993, designing a regional diamond exploration program in Labrador, Canada, which resulted in the discovery of the billion-dollar Voisey’s Bay Ni-Cu-Co. In 1996, he returned to Arkansas to complete the economic evaluation of the “Crater of Diamonds” State Park. Dennis completed a PhD on the Arkansas diamondiferous lamproites at the University of Texas at Austin in December 2002. Since 2004, he has been teaching geology and environmental sciences at Austin Community College.
In 2008, Dennis was hired by UT Natural Sciences to help write the new earth sciences portion of a four-semester, discovery-based integrated science curriculum for pre-service elementary school teachers. In 2013, this department became UTeach Primary and Dennis continues to teach the physics, chemistry, and geology portions of the curriculum. UTeach Primary also provides professional development to local school districts.