Introduction

Chalcedony, also known as Agate, is a microcrystalline form of Quartz that comes in many different colours, and ranges from translucent to opaque. It has been used in jewellery for thousands of years. From the Romans, to the Victorians, it can be found in jewellery from all over the world. While in the Gemmological world Chalcedony is the official name, in the jewellery world Agate is the term more widely used.
Many different varieties of chalcedony are used in jewellery, below we take you though some of the most popular ones found in our own collections.

Chalcedony comes in many colours, as in these earrings where we can see green chalcedony (or agate, as it is more commonly known) accented by blue and white diamonds.

Varieties Of Chalcedony

Agate

The official form of agate is a banded mineral, with different layers of colours on each level. This is a natural occurrence from different minerals being available in the formation process thousands of years ago. In jewellery it is often carved into cameos or signet rings, to make full use of the beautiful layers. Because of the individual make up of each agate, no two stones are the same. Sardonyx is the variety of agate that is specifically banded with white and brown or red layers, and jasper is the fully opaque variety, usually without banding.

Bloodstone

A deep green form of chalcedony, speckled with red spots on the surface of the stone, giving Bloodstone its name. In medieval times it was seen as a holy stone by Christians, the red on green was thought to represent Christ’s blood on grass.

Agates are usually carved to make full use of their natural layers of colour, as in this antique cameo brooch.

Carnelian

Carnelian is the red, orange, or amber coloured variety of chalcedony. Often solid in colour, carnelian can also have natural banding, as in agate. Carnelian was one of the most highly revered stones in antiquity, carnelian jewellery has been found along the ancient Silk Road. Sard is the brown variety of chalcedony, and is often interchangeable with carnelian, however sard is rarely used in jewellery.

This Art Deco pendant features a carved carnelian, with diamond detailing.

Moss Agate

Moss agate is not a variety of chalcedony, rather a type of agate. Like the name suggest, a green moss like pattern can be seen in the agate but the colouration is not created by vegetive growth. Dendritic agates also displays vegetative features, including fern-like patterns but usually these are dark brown or black in appearance.

Moss agate has distinctive moss-like patterns in the stone. In this antique pendant it has been cut to show the full effect.

Wear & Care

Agate in general is quite hard wearing. The stone has a 6.5-7 rating on the Mohs hardness scale and does not scratch very easily. Care should be taken if wearing agate rings, as hard wear can chip the stones and hard blows can cause the stone to crack.

To clean agates use a soft clean cloth and wipe it down, if more cleaning is needed use warm soapy water and a soft toothbrush. Pat dry with a soft cloth.

If in doubt, please feel free to Contact Us, and our gem experts can advise you.

Onyx

Onyx is the black variety of chalcedony, but can also have black and white banding in the stone. Often in the jewellery trade onyx is the term used for any chalcedony with a solid colour. Onyx became very popular in the Victorian period and can often be seen in mourning jewellery. Later on, the monochromatic themes of the Art Deco movement made huge use of onyx and its deep black colour.

This Art Deco stud set uses diamond and onyx to create a monochromatic colour scheme.

History

Agate derives its name from a river in Sicily, the Greeks called Achates. Vast quantities of agate were discovered in this river as early as 300 B.C. The term chalcedony is derived from the name of the ancient Greek town Chalkedon, which can now be found in modern day Istanbul.

In Ancient Egypt, grey agates were often worn around the neck to protect against and heal stiff necks. Ancient Romans believed moss agates to have "divine" power. Ingredients for lotions and ointments were ground on moss agate to infuse the treatments with the stones healing properties.

In the Middle Ages wearing agate was thought to cure insomnia and ensure sweet dreams.

During the reign of Queen Victoria, Scottish agate jewellery became the height of fashion, these pieces are highly sought after by collectors today.
In the 1920s and 1930s onyx became very popular to use in jewellery because of the movements monochromatic themes.