Okay so I need a Flawless Ruby.
For the Peryite quest.
Does anyone know of a location where there definitely is one?

5 guaranteed gems are found in 5 different locations:

• The Emperor's Quarters on the http://uesp.net/wiki/Skyrim:The_Katariah (http://uesp.net/wiki/Skyrim:Haafingar)
  
• http://uesp.net/wiki/Skyrim:Korvanjund_Crypt (http://uesp.net/wiki/Skyrim:The_Pale)
  
• 430 ft NNW of http://uesp.net/wiki/Skyrim:Reachwater_Rock (http://uesp.net/wiki/Skyrim:The_Reach) (x=-145834, y=4272) Go downstream in the river near by and you will find a row boat to the right. It's sitting inside the rowboat.
  
• http://uesp.net/wiki/Skyrim:Shriekwind_Bastion (http://uesp.net/wiki/Skyrim:Falkreath_Hold)
  
• http://uesp.net/wiki/Skyrim:Amaund_Motierre in http://uesp.net/wiki/Skyrim:The_Bannered_Mare (http://uesp.net/wiki/Skyrim:Whiterun) carries one.
  
  
  Try jewellery merchants as well.

Oh okay, awesome! I have to go to Shriekwind Bastion anyway! Thanks.

No problem, I simply searched UESP for them, fantastic site if you need to find something like this and probably a lot quicker than asking for it on the forums.

True, I know of it and have used it plenty of times. Was just feeling lazy, apologies. Lol