Coloured engagement rings are hot now. Good news is many of them are cheaper than white diamonds. If you love the romantic shade, you're in luck…there's so many types of pink rocks to choose from. Here are five of the most common.

Kunzite

Named after George F. Kunz, Tiffany & Co.'s chief gemologist and noted mineralogist who discovered it in 1902 and identified it as a new gem variety of the mineral spudomene. It has a hardness of 6.5 to 7, and comes in pink and light purple colours.

Morganite

From the same beryl family as the aquamarine and emerald, the morganite exhibits a soft peach, pink or purple shade. It was discovered in 1910 and shortly after named by George F. Kunz in honour of banker John Pierpont "J.P." Morgan, who was a gemstone collector and one of Tiffany & Co.'s biggest customers. It has a hardness of 7.5 to 8.

Pink Tourmaline

Tourmaline is not a single mineral but a family of closely related ones that occur in an amazing array of colours. They include the popular pink, green, blue, red, brown and multi-coloured ones. Tourmalines that exhibit a lush pink to rich crimson are called rubellites, and the way they are distinguished from other red and pink tourmalines is from the way rubellites behave in daylight and artificial light – they holds their colour when the light source is changed. This family of gems has a hardness of 7 to 7.5.

Pink Sapphire

The mineral corundum gives us two kinds of gemstones: the red ruby, and sapphires of all colours, from blue to other hues like colourless to yellow to pink. The most valuable varieties are the cornflower blue, the orangey-pink colour Padparadscha, as well as colour-changing ones. It has a hardness of 9.

Pink Spinel

The spinel has a hardness of 7.5 to 8, and comes in a rainbow spectrum of colours, from red and lavender to grey and black. The most precious is the red, which has been mistaken for the ruby in antiquity, for both look alike and are found in the same regions. It is not until technological advancements were made in the gemology field in modern times that certain famous old rubies were found to be spinels, one of which was the Black Prince's Ruby.