Here's why:

* Gold is a noble metal: Gold is highly resistant to chemical attack, including by most acids. This is because it forms a protective oxide layer that prevents further reaction.

* HF's reactivity: While HF is a strong acid, it primarily reacts with metals that form fluoride salts (e.g., silicon, aluminum).

* Aqua regia: The only common acid mixture that can dissolve gold is aqua regia, which is a mixture of concentrated nitric acid and hydrochloric acid. This is because nitric acid acts as an oxidizing agent, and the hydrochloric acid forms tetrachloroaurate(III) anions ([AuCl₄]⁻) with the gold ions, which helps to remove them from solution.

However, there is a caveat: HF can etch gold in the presence of oxidizing agents. This means that if HF is combined with an oxidizing agent like nitric acid or chlorine, it can slowly attack the gold surface. This is not a common process, but it can occur under specific conditions.

Therefore, in general, you can consider gold to be relatively inert to hydrofluoric acid.