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?
If you go back 50 years gold price always stable. It price Don't changes huge. If you go back 5 years bitcoin price huge increase. Yes it price can be huge down but not it possible 500$ cause today world economy effected in bitcoin price. Today if you buy gold after years you get some profite but bitcoin can give you huge profits.
This instability is due to the amount of supply held by several large investors, so that the movement of bitcoin can rise very high and fall rapidly. Of course this is different from gold, where the value is taken from the price of mining oz, so that the movement is not too far away.