Serious and Regal

Maria Doyle Kennedy portrays Catherine of Aragon in "the Tudors" wearing this gorgeous dark gown. Personally, I think this is the most beautiful dress worn by "Catherine" in the entire show. The main fabric of the gown is of a lush black velvet. The bodice and the petticoat are beautifully embroidered with a silver/grey thread adorned with bright pearls.

Close-up of the embroideries

It is hard to see in most shots of the episode but the sleeves beneath the velvet is closely ruffled to the wrist.
The neckline has not been decorated with jewels or a different fabric but the magnificent jewels of gold, onyx and rubies makes up for that in every way.

Close-up of the ruffled wrist