WHAT GOLD DOESN'T TARNISH?
In its pure form, 24k pure gold does not rust or tarnish as it does not combine with oxygen easily. In fact, pure gold holds the title as being one of the elements that is least reactive to oxygen. This is why pure gold retains its luster.
When it comes to gold jewelry, it is very rare to find pure gold pieces. Gold in its pure form is not suitable for jewelry use because of its intense softness, which leads to easy scuffing and scratches. It is typically alloyed with other metals in order to be formed into strong, durable jewelry. The alloy metals mixed with the gold usually have properties that make the piece tarnishable. This is why, if not properly cared for, gold jewelry may tarnish.