I would say emerald. It's far rarer than gold.
Rhodium and platinum are both more valuable than gold.
platinum
Linen is worth more than gold to a lot of people. Others would argue that gold is far more valuable.
gold is an inanimate object/substance... slaves get sh*t done.
The price of gold is probably increasing because there's less of it than there used to be and the more rare something is, the more valuable it is. try this site its useful http://gold-price-blog.info/
It is more valuable than gold because there is a few amount of gold and more dirt. So it is easy to find dirt than it is to find gold. That is why gold is more valuable than dirt.
Rhodium and platinum are both more valuable than gold.
Gold
There are several metals more valuable than gold. Platinum is one.
emerald most definitely has more cheats
Gold
yellow gold
Gold is more valuable than silver. durr.
An emerald with a blue tint is more valuable than one with a yellow tint.
i don't have emerald but the valuable Pokemon is rayquaza
pure gold (24k) vs 41.7% (10k) gold.. you decide.
platinum