Banded agates are a popular gemstone known for their unique and striking patterns. However, due to their popularity and unique appearance, banded agates are frequently mislabelled or sold as fakes, making it difficult for collectors and enthusiasts to find genuine specimens. In this blog article, we’ll explore some of the most popular types of banded agates, including their unique characteristics and how to spot fakes or mislabelled specimens. Whether you’re a seasoned collector or new to the world of gemstones, this guide will help you navigate the market and find the perfect banded agate for your collection.
Banded Agate / Sardonyx / Onyx
When you see bands link this, they will be either of the following:
- Onyx – a banded agate with alternating bands of black and white or other colours, often found in Brazil, India, and Madagascar.
- Sardonyx – made of Sard and Onyx, a banded agate with alternating bands of white or light-coloured chalcedony and darker onyx, often found in Brazil, India, and Madagascar.
Carnelian and Sard are both varieties of chalcedony that have a reddish-brown to brownish-red colour. The difference between the two is mainly due to the amount of iron oxide present in the mineral.
Carnelian is a type of chalcedony that is coloured by iron oxide and has a reddish-brown to orange colour. The iron oxide content of carnelian is relatively low, which gives it a lighter and brighter colour than Sard. Red and White Sardonyx is often sold as Carnelian, but they are not the same mineral. Carnelian sometimes has bands of similar colours, not alternating colour stripes which is typical of Sardonyx apperance.
Sard, on the other hand, has a higher concentration of iron oxide, which gives it a darker and richer red colour than carnelian. Sard is also often more opaque than carnelian, which can have a translucent to transparent appearance.
In some cases, carnelian can be heated to produce a darker, more reddish-brown colour that is similar to Sard. However, the resulting stone is still considered carnelian, as the basic composition of the mineral has not changed.
Madagascar Agate
Madagascar Agates: Madagascar banded agates come in a wide variety of colours, but they often exhibit bands of white, grey, brown, and yellow with black, brown, or orange bands. Madagascar banded agates are also known as Malagasy Agate.
When Madagascar agates are treated in this way and exhibit a distinctive reddish-brown and white banding pattern, they may be sold as Silk Agate (Synthetic Trade Name for colour enhanced Madagascar Agate) or Sardonyx. Sardonyx, which is made of Sard and Onyx, is a type of chalcedony that exhibits alternating bands of white or grey and brownish red. It is similar in appearance to other banded chalcedonies such as agates but has a distinct colour palette and is often used in jewellery.
Sardonyx
Sardonyx is a type of banded chalcedony, made of Sard and Onyx, that typically exhibits alternating bands of white or grey and brownish red. The brownish-red colour is due to iron oxide or hematite. Sardonyx is also known as Sardian Onyx.
Sardonyx is often sold as Silk Agate. Silk agate and sardonyx are both types of chalcedonies, a microcrystalline form of quartz, but they have some distinct differences.
Silk agate is a type of Madagascar agate that has been colour enhanced using a treatment that involves the use of silk threads. This treatment is sometimes referred to as “silk screening” or “silk dyeing”. In this process, silk threads are saturated with dye and then wrapped around the agate stone. The stone is then heated to set the dye, resulting in a permanent coloration that enhances the natural patterns and banding of the agate.
It’s important to note that colour enhancement treatments are common in the gemstone industry, and they can affect the value and authenticity of a stone. In the case of silk agate, the treatment is generally considered acceptable as long as it is disclosed and does not misrepresent the stone’s natural characteristics. If you are buying a silk agate or any other gemstone, it’s always a good idea to ask about any treatments or enhancements and to purchase from a reputable seller who can provide documentation and assurances about the stone’s quality and authenticity.
Overall, while both silk agate and sardonyx are types of chalcedonies with some similarities, they have distinct differences in appearance, composition, colour, rarity, and uses.
Botswana Agate
Botswana Agate: Botswana banded agate is a specific type of banded agate that comes from Botswana. It typically features muted shades of grey, pink, and brown bands. Botswana banded agate is also known as Botswana Agate.
Botswana agate is a type of banded agate that is primarily found in Botswana, a country in southern Africa, but it is not exclusively found there. Botswana Agate is actually a type of fortification agate, which is characterized by its distinctive banded patterns that resemble the walls of a fortification. This type of agate can also be found in neighbouring countries such as Namibia and South Africa.
The Botswana Agate is known for its soft, muted shades of grey, pink, and brown, and its banding patterns can be either parallel or concentric. The patterns and colours in Botswana Agate are believed to be created by the presence of iron and manganese oxides, as well as other minerals and impurities.
Overall, while Botswana is the most well-known source of Botswana agate, this type of agate can also be found in other locations in southern Africa. The high demand for this unique and beautiful stone has made it popular among gemstone enthusiasts around the world.
Fortification Agates
Banded Agates: The natural colour of agates varies widely, but banded agates exhibit alternating bands of various colours, such as white, grey, black, brown, red, orange, and yellow. Here are some ensamples of Fortification Agates
- Crazy Lace Agate – while technically not a true fortification agate, some types of crazy lace agate can have fortification-like patterns and are marketed under this name.
- Montara Agate – this trade name is often used for fortification agate found in California, particularly in the area around Montara Beach.
- Sagenite Agate – this term is used for fortification agate with distinctive inclusions of needle-like crystals, giving the stone a “frosty” appearance.
- Laguna Agate – this trade name is used for fortification agate found in the mountains of central Mexico, particularly around the town of Ojo Laguna.
- Botswana Agate – while not strictly a fortification agate, Botswana agate can have similar banding patterns and is sometimes marketed under this name.
- Plume Agate – another type of agate that can have fortification-like patterns, plume agate is named for its inclusions of feathery or plume-like formations.