You can find Dan in on the 2nd floor of the Courthouse in Quartz, being held captive. He is also a recruitable NPC.
Trivia[]
Dan Citrine is found in Quartz. Citrine a variety of quartz that exhibits a color ranging from pale yellow to brown.
If you have Dan Citrine when you open the cells in the Courthouse, you can get $1000 from his dad who runs out of one of the cells.