This web chat is now closed but you can read the transcript in full in the comments section, below.
New Zealand-born Jessica began creating her own jewellery pieces from an early age after growing up surrounded by antiques in father's auction house in Christchurch. She then embarked on an internship at Sotheby's London jewellery department, where she learnt about antique jewellery techniques that would become central to her own work.
Rihanna wore a pair of McCormack’s diamond Wing of Desire earrings in the music video for Live Your Life, while Madonna, Alexa Chung and the former French Vogue editor Carine Roitfield have also been spotted in her designs.
Since 2007, she has been based at her own appointment-only salon in London's Clerkenwell, where she has designed five diamond jewellery collections, including her latest, XIV. Every piece is handmade in London and the diamonds are sourced through ethical means.
Jessica said, "For me, making jewellery is about creating miniature sculptures. Each piece is the end result of my desire to turn what I perceive to be beautiful into a tiny piece of art. I would like people to re-evaluate their perception of fine jewellery and precious stones, breaking down barriers on how diamonds are considered, worn and used, with emphasis on luxury being about personal experience, appreciation and knowledge."
Along with designing jewellery, Jessica has also been working with Fashion Fringe, a platform which mentors and supports upcoming fashion talent, for the past three years creating a bespoke trophy for the winner. You can read more about Fashion Fringe here.
This masterclass is now finished but you can read all the questions and Jessica's answers, below.