Although often considered as a single type of common gemstone (typically red in colour), garnets are actually a family of related minerals that comes in an entire rainbow of colours.

From the deep red of the pyrope garnet to the dazzling orange of spessartite to the vivid green of tsavorite, there is a colour for everyone. In fact, the wide spectrum of garnet colours includes red, orange, yellow, green, purple, brown, blue, black, pink and colourless.

Members of the garnet group (with their common colours) include:

• almandine (red, brown-red, violet-red)
• spessartite (yellow, orange to reddish-brown)
• pyrope (purple-red, pink-red, crimson, deep red)
• grossular (colourless, yellow, yellow-green, green, brownish-red, orange or black)
• andradite (colorless, yellow to green or brown to black)

Whilst all types of garnet possess similar physical properties and crystal forms, they differ in chemical composition and this is what gives them their colour range.

The rarest of the colours is the blue garnet (a mix of pyrope and spessartite), which was discovered relatively recently in the late 1990s in Madagascar. It can command prices of around £1000 per carat.

Commonly regarded as the most prized garnet is an emerald-green variety called demantoid, which is a member of the andradite group and has an incredible lustre, very similar to that of diamond.

Garnets have been used in jewellery for millennia and ancient Egyptians wore pieces with garnet inlays. The gemstone was also popular in Roman times and the name is thought to come from the Latin word granatus, meaning seed, due to the similarity of the stone’s colour to the seeds of a pomegranate. The various types have a range of hardness on the Mohs scale of about 6.5 to 7.5, meaning that they are quite resistant to scratching.

Garnet (in particular red garnet) is the birthstone for January and is believed to signify eternal friendship and trust, making it a perfect gift for a close friend. Many people think that garnet is also associated with success in business.

Amongst the most important sources for garnet currently are several countries in Africa, Sri Lanka, India, Brazil and the United States.