These are another new feature. Gems can either be looted from the bodies of dead monsters or produced when touching a gem shrine. Gems can be placed in socketed items such as shields, armour, weapons and helms to enhance various attributes. They can not however, be placed into magical or rare items. Once a gem has been placed in a socket it can not be removed though, so careful consideration needs to be paid to what type of item you are 'building' before committing to the placement of a gem.
Gems produce different effects depending on which item it is placed in.
An example would be a Chipped Amethyst which will improve the chance to hit of a weapon, raise armour rating of a shield and in a helm will improve strength. The maximum number of sockets in any item is 3 and you do not need to place the same gem types in an item, you can mix and match. For example, one item we found had three gem sockets and was enhanced with 3 types of damage. The better quality your gem the greater the benefits. All gems can be upgraded to further enhance their properties, prior to placing into an item socket, by way of Gem Shrines which are randomly generated and appear in around one shrine in 3 or 4 games.