This workshop was attended by SEG UGM-SC member and former. The workshop was be held on April 20th, 2017 at Optical Geology Laboratory, began at 7.00 pm and end at 9.00 pm. Renaldi Suhendra, the former member of course and workshop division SEG UGM-SC 2015 became the speaker. This workshop held to discuss about alteration petrographic analysis. The participant was really interest to the topic and very active joined the discussion also identified the alteration mineral from thin section.