pixel_player47340819 if i recall correctly his first arrival brings 100 gems then afterwards its kinda random a few gems here and there but mostly hyperloop mats...there is a chance at 10,,50,100 and even 500 gems from him but as you can imagine the most gems are rare....though i just received 50 from him tonight 🙂
http://trainstation.wikia.com/wiki/Chris_Reward_Set