The formatting might still be improved, but here's the info dump for ya. These are from Pristine Quality shards.
Magic+Magic Sorcerer's Gem +1 all unlocked Sorcery skills
Magic+Lightning Gem of Abatement -20% Mana Cost
Magic+Fire Gem of Abatement -20% Mana Cost
Magic+Ice Gem of Abatement -20% Mana Cost
Magic+Physical Warrior's Gem +1 all unlocked Might skills
Magic+Protection Gem of Enlightenment +1 to all first four tier skills
in all trees
Magic+Poison Rogue's Gem +1 all unlocked Finesse skills
Lightning+Lightning Gem of Tempest's Vengence 75% chance to shock enemies when Attacked
Lightning+Ice Gem of Magic Resonance +20% Lightning, Fire, and Ice
damage
Lightning+Physical Gem of Opulence +20% gold drops
Lightning+Fire Gem of Magic Resonance +20% Lightning, Fire, and Ice
damage
Lightning+Protection Gem of the Assiduous +8% more experience
Lightning+Poison Gem of Unrivaled Vitality +50 HP and MP
Ice+Ice Gem of Winter's Vengeance 75% chance to freeze enemies when Attacked
Ice+Physical Gem of Opulence +20% gold drops
Ice+Fire Gem of Magic Resonance +20% Lightning, Fire, and Ice damage
Ice+Protection Gem of the Assiduous +8% more experience
Ice+Poison Gem of Unrivaled Vitality +50 HP and MP
Physical+Physical Gem of the Subjugator +15% Damage and +10% damage
resistance
Physical+Fire Gem of Opulence +20% gold drops
Physical+Protection Gem of the Enlightened +10% experience
Physical+Poison Gem of Opulence +20% gold drops
Fire+Fire Gem of Summer's Vengeance 75% chance to burn enemies when Attacked
Fire+Protection Gem of the Assiduous +8% more experience
Fire+Poison Gem of Unrivaled Vitality +50 HP and MP
Protection+Protection Gem of Paralyzing Vengeance 60% chance to stun enemies when Attacked
Protection+Poison Gem of the Assiduous +8% more experience
Poison+Poison Gem of Plague's Vengeance 75% chance to poison enemies when Attacked
Best Answer
On the console (Xbox 360 in my case) it autosaves every time I zone change, including going in and out of houses. The PC version may be a bit more liberal with autosaves, but I can't see is as by much more than that.