I know this is old but I stumbled upon it in my search for the same books, so I'll answer anyway. I believe the ones you are looking for is the A Tale of Eron series by Tom Deitz.
In the icy northern realm of Eron, three young artisans bound by an unspeakable act of violence arrive at an isolated gem mine on a special commission for their king. They are the arrogant but talented Eddyn; Avall, his archrival; and beautiful Strynn, newly wed to Avall, but carrying Eddyn's child.
Meanwhile, to the south, amid Ixti's scorpion-riddled sands and sensuous cities, a horrible accident has forced Prince Kraxxi into exile with blood on his hands and a price on his head.
The four will be drawn together--and torn apart--by a magnificent find: a gem with magical properties beyond anyone's imagining or control. It is a struggle in which hidden forces pursue a frighteningly sinister agenda. For whoever possesses the gem holds the future of the world...and the power to destroy it.
