Precious stones are going to be a good type of investments because they are really have high value in the market and as the time goes by.
Their value is keep on appreciating and the same I think with bitcoin that it is also increasing its value as the time goes by.
But I would bitcoin rather with gold, because its volatility is impressing me.
They are promising investments and they are both profitable.
Earnings and profits are the main key in choosing what kind of investments people preferred to. If they think they can go with the flow of all the risk associated in their chosen investments then just go with that kind of investment.