Shares of Saudi Aramco surged on their second day of public trading, pushing the kingdom's record IPO to a gargantuan $2 trillion valuation and briefly touching Crown Prince Mohammed bin Salman's long-held target for the company.

Share rose 10% to 38.7 riyals apiece ($10.32) but slipped back to 37 riyals within minutes of the market open.

The figure, nearly $1 trillion higher than the world's next-largest public companies Microsoft and Apple, was long ridiculed and regarded with disbelief by much of the international financial community.

Riyadh on Wednesday made history by listing 1.5% of its state-run oil giant on its local stock exchange, the Saudi Tadawul, in what was the largest IPO on record. Shares went limit up, rising 10% in price as trading started, giving the company a valuation of $1.88 trillion on its first day of trading.