By Åse Anderson
If you're planning to pop the question on the most romantic day of the year, don't be afraid to be creative when it comes to finding a unique engagement ring.
The classic diamond's status as "a girl's best friend" is being challenged by a rainbow of other gems, and coloured stone engagement rings have become a highly desirable alternative. Not every girl dreams of a traditional white diamond solitaire, so if you know that your bride-to-be's tastes are more offbeat, choose a unique engagement ring to suit her personal style.
Kate Middleton's sapphire ring, which once belonged to the late Princess Diana, set the trend for engagement rings with coloured stones, and celebrities such as Angelina Jolie and Penelope Cruz have also been spotted wearing sapphires and emeralds.
Red rubies and blue sapphires are the obvious go-to gemstones for those seeking a colourful alternative to diamonds. While they are undeniably beautiful, it is worth bearing in mind that their rising popularity has been matched by a steep increase in prices. If you do opt for a ruby or sapphire engagement ring, the design options are not limited to a simple solitaire. The striking Sabine G ring features a ruby nestled in-between two heart-shaped diamonds while Emma Franklin's sapphire engagement ring is flanked by mink diamonds and baguette-cut white diamonds. Sapphires also come in a variety of colours, including pink, yellow, green and purple, as seen on the Swirl purple sapphire engagement ring by ethical jeweller Ingle & Rhode.
Red spinel is a great alternative to a ruby. The emerald-cut spinel in this Tiffany & Co. Soleste ring is saturated with a rich colour that really pops against the bead-set diamonds.
From tsavorites to morganites, there is a wealth of beautiful gems in vibrant colours or more subtle hues that make stunning centre stones for unusual engagement rings.
What could be more appropriate for Valentine's Day than a heart-shaped engagement ring? The rich purple hue of the amethyst heart in Wright & Teague's engagement ring looks opulent against the gleaming yellow gold, while the light green tsavorite garnet in Theo Fennell's extravagant design sparkles with an iridescent luminosity.
Beautiful, stylish and unusual, the Emma Franklin engagement ring set with an emerald-cut tourmaline, suspended between two gold bands studded with diamonds, ticks all the boxes for the bride-to-be who wants to stand out from the crowd.
With a floral motif picked out in pink sapphires and green tsavorite garnets, the pretty engagement ring by ethical jeweller Erica Sharpe is perfect for a warm weather wedding.
For a more classic take on a unique engagement ring, the Astley Clarke morganite ring has a romantic feel, with the central stone surrounded by glittering pavé diamonds in a vintage-inspired halo setting.
Now that we've opened your eyes to the colourful world of engagement rings, all you have to do is pick your stone and cross your fingers that she says "yes". For more advice on buying an engagement ring, click here.