Something that's aurous is made of gold. You could describe your favorite gold necklace as aurous, but you might sound more like a scientist than a jeweler if you do so.
While you can use the adjective aurous to describe something that contains or is made of gold, it is most commonly used in scientific language that mentions the chemical compositions of elements made of or derived from gold. A chemical compound that contains gold is an "aurous compound," for example. Aurous comes from the Latin word aurum, or "gold," and its chemical symbol is Au.