We had a member that did extensive testing and came up with this guide for us to use
MIXED TRANSMUTE
If you combine separate types of items (gems, metals, relics) you get a new item based on the total value of the items transmuted.
Under 200 Common, uncommon, or rare seed with average quality of Nice
201 - 499 §350-700
500 - 999 22-40 Ancient Coins
1000 - 3499 A Magic Gnome
3500 - 4999 Uncut Tiberium
5000 - 11999 Fragment of Pushable Statue, Dive Well, Plain Sarcophagus, Egyptian Sarcophagus, or Sarcophagus of the Kings
12000 - 24999 Fragment of Sarcophagus of the Kings
25000 - 49999 §22000-27000 bottle of nectar, 100-200 years old
50000 - 99999 §45000-55000 bottle of nectar, 300-500 years old
100000+ §75000-110000 bottle of nectar, between 700-900 years old
located in this thread,
http://www.carls-sims-3-forum.com/index.php/topic,747.0.html