Hi, I am new here and also very new to working with precious metals. I am a knife maker and welder so I know my way around metal work, even intricate things but have never worked with gold.
I have been asked to repair a hairline crack in what I am almost sure is a golden chalice. It is at the base of the cup where it meets with the stem.

My questions are, how can I better tell what material it is and how should I go about the repair?

From my research, I am thinking the best route would be using easy solder paste and a torch. I also see that I should get it very clean, what is the best way to clean it?

Any and all pointers are appreciated my. If you think I'm crazy for attempting this, let me know

Thank you!