Soul Gem (Skyrim)

Soul Gems
soul gems are primarily used for enchanting your weapons at an arcane enchanter or use the soul gem to charge your enchanted weapons.

Purchasing soul gems
you can buy filled soul gems from merchants directly. However, this is an extremely expensive proposition, as a filled gem is three to four times the price than if you were to buy an empty one.

Finding soul gems
An even better option is to find (or steal) the soul gems from there are also a number of soul gems that can be found at the College of Winterhold
 * Dwarven cities
 * Warlock Den
 * Vampire Lair
 * Nordic ruins

soul gem types
soul gems are separated into types based off of the capacity they can carry. The soul gem types are petty, lesser, common, greater, grand and black.

Black soul gems
Black soul gems can only be used for gathering human souls such as Note: falmer do not count as an npc
 * NPCs
 * Bandits
 * Forsworn