What compound was considered more precious that gold in ancient Rome?

i think it's aluminum, i found it in google

In my Google search, there was no mention of aluminum as a precious metal. Rather silver, gold and bronze were mentioned, especially in relation to use in coins.

http://www.crystalinks.com/romecoins.html
http://penelope.uchicago.edu/Thayer/E/Roman/Texts/secondary/SMIGRA*/Argentum.html
http://www.deadromans.com/coins/default.htm#Metals%20and%20Denominations
http://www.abc.net.au/science/news/stories/s913237.htm
http://www.answers.com/topic/precious-metal

I don't know if this will help or confuse things more for you, but I hope it helps. Thanks for asking.