TrueLoaded is a great platform to build a jewellery website. It has a number of features specifically created for jewellery industry that are now available with TrueLoaded:

Choosing Powerful Commerce to build your merchandise online store allows immediate access to a number of great features for this type of website:

• RapNet integration - RapNet is #1 diamond sourcing tool internationally, and Powerful Commerce can be easily integrated with it, to receive its up-to-date catalogue of available diamonds and add margin to it 
• Design your own ring - to allow users design their own diamond engagement rings or wedding bands, using various parameters in a special "wizard"
• Properties and filters - allow you to describe products using vairous properties (colour, material, gender, size, occasion, etc) and then users find the best product matching their criteria in just a couple of clicks 

www.sugarohhoneyhoney.com is a great example of jewellery Ecommerce website based on Powerful Commerce