Birthstones by month

Garnets are a family of gemstones. The two best-known varieties are pyrope and almandine, both of which are red.

They were used in late 18th century ‘Bohemian’ jewels, in foil-backed settings.

Other varieties include golden hessonite and vivid orange spessartine. Green garnets include demantoids, first mined in Russia in 1868, and tsavorite.

The deep purple is due to a combination of iron and other metals within its crystal structure, and natural radiation.

The resulting hue is associated with royalty and wine, with amethyst thought to protect against intoxication.

Until the 18th century, amethysts rivalled sapphires, emeralds and rubies in value.

The colour of sea water, the pale blue or blue/green beryl is said to protct sailors.

In contrast to emeralds, aquamarine is often found in relatively large, clean crystals, the most famous source being the Santa Maria mine in Brazil.

Diamond gets its name from the Greek 'adamas', meaning 'unconquerable'. It's so hard, it can only be cut with the help of another diamond.

Originally found in river beds, they were only mined from the late 1860s.

Diamonds are rated on the 4 Cs: color, clarity, cut and carat weight.

Now associated with youth, emerald mining dates back to 1500 BC in Egypt.

Emeralds are another type of beryl and derive their extraordinary green from chromium impurities.

Emeralds rarely form without without inclusions (materials inside) but, unlike in other stones, these are celebrated.

A symbol of purity and honesty, pearls are the only gem formed within living creatures. They are said to bring good luck and wisdom.

Alexandrite is also considered the birthstone of June, but rare among antique rings.

The red varieties of the mineral corundum are called rubies and coloured by the element chromium. All other colours are known as sapphires.

Second only to diamond in value by carat, they are known as the king of gems and associated with love and vitality. Burmese rubies are particularly highly prized.

Peridot is formed deep below ground and brought to the surface by volcanos - it's also arrived on earth via meteorite. It's associated with warding off nightmares and known as the evening emerald.

Naturally green, but sometimes with yellow or brown tints, it's an 'idiochromatic' stone and its colour is not due to chemical impurities, as with 'allochromatic' sapphire and ruby.

Sapphires are the mineral corundum. You might think blue but they come in any colour except red (when they are called rubies).

Formed by an intricate interplay of iron, titanium and vanadium impurities, they were associated with holiness in the medieval era and a popular choice for ecclesiastical rings.

Every opal has a pattern of its own. The iridescence is due to light interacting with a network of spherical silica structures.

Blue and green are most common with orange and red rarest. Patterns also vary - small flashes of 'pinfire' colour vs broad contrasting colours, known as harlequins.

Tourmaline is an alternative birthstone for Octover.

Associated with wealth, and coming in a rainbow of colours, topaz jewellery reached its peak in the 18th and early 19th centuries.

The other birthstone for November is yellow citrine, symbolising the sun and life - they were particularly popular during the postwar Art Deco period.

Zircons are fascinating and historic stones, prized for their unusually bright lustre and high dispersion, rivalling that of diamond.

They come in vivid colours from rich gold and sherry tones to deep greens and swimming pool blues - it's blue zircons that are the birthstone for December