GOLD TEST
Fire test
Real, pure gold, when exposed to the flame, will get brighter after a while as it gets hotter, but will not darken.
Scratch test
Real gold will leave a gold-colored marking, which other metals will just leave a black streak.
Acid test
Gold is considered a noble metal, which means it is resistant to oxidation and corrosion from acids. This is why it shouldn’t change color when it comes into contact with your skin, vinegar, or nitric acid.