Gold is another store of value, but not that unstable. It reached 2000$ recently and was above 1000$ for many years. Those who invested in gold back in 1900 would have made a great choice since it costed only 20$ back then if I'm not wrong. (Although dollar was way more strong than now)
Bitcoin can lose 500$ within one night. Gold can't. Why that?
You have to take into account many factors, although bitcoin has a lot of similarity to gold.
1) Gold has been used for hundreds of years as a value asset, in recent years it has become a liability but its value is stable basically because its market is already mature.
2) Although bitcoin is perhaps at its highest peak since its creation, it has not yet diversified enough to be stable, for example if you look at more than 65% of circulating bitcoin are in the first 50 wallets. What does this mean? that large holders move the price to their advantage, so probably once you find a fair distribution the market will be "stable".