The Sirius Star diamond, named after the brightest star in the sky, is the brightest, most brilliantly cut Canadian diamond on the planet. It's patented design delivers unparalleled brilliance because of it's patented cut delivers amongst the highest 'light returns' of all diamonds, Light return is a measure of the amount of light that enters a diamond vs the amount that is reflected and refracted back. When you look at a diamond's 'sparkle' what you are seeing is the light return. The Sirius Star diamonds are the brightest of all (Canadian or otherwise) diamonds in the world.
We have a wonderful video on this site that explains why these diamonds are so prized. You can find that video here.