 Agate 157
Portrait - From £15.20
In many banded agates where there is insufficient material to fill the entire cavity the centre is fully or partially (as in geodes) filled by quartz. Here, translucent white quartz, tinged salmon pink by agate below, has formed between different zones of intensely coloured agate. Size: 6cm.
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Agate 158
Portrait - From £22.80
The mysterious formations at the bottom of this image are taken from the edge of a banded agate. The banding above has been disturbed by what is probably a hemispherical agate 'eye' - but who knows what processes led to the singular shapes that caught my eye. Size: 4cm.
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Agate 159
Square - From £30.40
This image is taken from close to the perimeter of a banded agate. Some of the formations appear to be typical 'hemi-agates', but how the dominant peach-coloured egg-shaped feature arose is not clear. The dominant dark blue colour is probably the result of titanium, copper and manganese. Size: 2.5cm.
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Agate 161
Landscape - From £19.00
The 'level-banded' formations that feature in the centre of many banded agates are referred to as 'onyx'. Tiny quantities of impurities and changing conditions as the layers build up can lead, as here, to formations that are strikingly like land- and seascapes. Size:5cm.
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Agate 160
Landscape - From £15.20
This banded agate exhibits the classic 'fortification' formation - name after the resemblance to Baroque defensive structures. The bands are crossed by a blizzard of small marks whose origin is obscure, but may be due to microscopic stree-relief fractures. Size: 6cm.
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Agate 153
Square - From £30.40
This detail from the perimeter of a banded agate shows a series of tiny 'hemi-agates' billowing out from the narrow bands of chalcedony whose crystallisation is the first stage in agate formation. The colour banding here is weakly marked except where the bands have been distorted into the flame-like form. Size: 1.5cm.
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Agate 148
Square - From £30.40
Brazilian agates, such as this speciment from Minas Gerais, are renowned for their occasional 'wild' formations such as this. It probably results from a combination of pressures and stresses acting before and after crystallisation, but is impossible to explain in detail. Size: 4cm.
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Agate 147
Portrait - From £15.20
When there is insufficient material to fill the pockets in rocks in which agates form the central void is typically filled either by quartz or, as here, by horizontal bands crystallised from a second infusion of silica. Size: 6cm.
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Agate 146
Portrait - From £11.40
When there is insufficient material to fill the pockets in rocks in which agates form, the central void is typically filled either by quartz or, as here, by horizontal bands that crystallised from a second infusion of silica. Size: 6cm.
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Agate 149
Square - From £30.40
These parallel bands of colour formed under the influence of gravity to fill the void in the centre of an agate in which there was insufficient material to fill the rock void with concentric bands. The bands are subtly and exquisitely coloured. Size: 4cm.
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Agate 152
Landscape - From £22.80
The banded formations of this agate are a wildly distorted version of the classic 'fortification' type. The distortions are thought to be the result of internal forces operating prior to crystallisation, but their precise nature is not understood. Size: 7cm.
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Agate 151
Portrait - From £15.20
This image features a narrow slice from the perimeter of a banded Madagascan agate through to the crystalline white quartz that partially fills the void at its centre. The 'eye' at the bottom is a circular section through what is almost certainly a hemispherical formation. Size: 6cm.
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Agate 150
Square - From £30.40
This detail from a large slice of Brazilian agate is formed of a brilliant orange 'island' of agate surrounded by what appears to be a dark brown 'moss' agate, most likely consisting of manganese oxide, and this in turn is ringed by crystalline quartz. Size: 2cm.
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Agate 162
Portrait - From £15.20
This is a detail from an American Maury Mountain Moss Agate that shows none of the 'classic' agate banding. The sweeping, red-orange mossy 'foliage' is formed by the crystalline growth of impurities - the colour here suggests that it is likely to be iron oxide. Size: 4cm.
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Agate 163
- From £30.40
This is a tiny area from a large piece of a wonderfully-named American Flame-tail Rooster Agate. The brilliant-red 'vegetation' is the source of its generic name, moss agate, and is formed by crystalline growths of impurities such as iron oxide. Size: 3cm.
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Agate 173
Landscape - From £22.80
This images, scanned with transmitted light from the perimeter of a banded agate, shows an island of quartz framed by the concentric rings of agate 'eyes', which are generally the result of slicing through hemispherical formations that typically develop near the outer surface. Size: 3cm.
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Agate 176
Square - From £30.40
Shapes such as this, formed by the meeting of several banding systems within a 'fortification' agate, are common. What make this unusual is that the resulting plane is dramatically highlighted by colour forming between the bands. Size: 2cm.
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Agate 109
Square - From £30.40
This image shows all the classic quartz features: perimeter and horizontal banding framing a small area of quartz. The brown formations with their radiating spikes that single it out from countless similar specimens are probably the result of silica replacing an inclusion of another mineral. Size: 1.5cm.
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Agate 177
Square - From £30.40
This agate shows an unusual combination of concentric and level banding. Such confusion would hardly appeal to an agate collector, but it makes for a compelling visual images. Size: 8cm.
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Agate 171
Square - From £30.40
This images shows the central area of AG169, an unusual banded agate featuring the kind of complex, hard-to-explain formations that are a speciality of Brazilian agates. The striking difference in colour is due to this being produced by reflected not transmitted light. Size: 5cm
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Agate 170
Landscape - From £22.80
This is a detail of AG169 and features the kind of complex, hard-to-explain formations that are a speciality of Brazilian agates. Size: 3cm
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Agate 165
Landscape - From £19.00
Parallel bands such as these form when a void is left at the centre of the developing agate following the formation of concentric banding. The later bands form horizontally under gravity from a secondary infusion of liquid silica. Size: 6cm.
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Agate 164
Panoramic - From £13.30
Fascinating details in agates often occur early in their formation near to the surface of the host rock. The 'hemi agate' fomations here - also known as 'eye' agates - are slices through spherical structures and strikingly different in colour to the chalcedony that fills most of the void. Size: 3cm.
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Agate 167
Square - From £30.40
This Madagascan agate shows many classic features: concentric banding; 'eyes' sliced through hemispherical formations; the ends of hollow tubes that formed around inclusions of other minerals such as rutile or geothite; and areas of crystalline quartz. Size: 7cm.
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Agate 168
Landscape - From £19.00
The development of the concentric bands in this agate must have been subject to various disturbances before, and possibly after, crystallisation to create this complex series of formations. Size: 7cm.
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Agate 107
Square - From £30.40
The other side of this 3mm thick slice of a level-banded agate is dominated by two large 'eyes' fringed with brown. On the reverse, seen here, all that remains is their ghostly presence, grinning through the loosely defined banding structure.
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Agate 169
Square - From £30.40
Agate frequently frames a quartz-filled void, but here this is reversed. The whole slice consists of a very narrow band of agate framing a large area of quartz at the centre of which is this exquisite formation, seen in more detail in AG170. Size: 10cm
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Agate 142
Portrait - From £15.20
The dominant formations here appear to result from an 'agate dyke' that is thought to form to release excess silica back into the host rock due to the build up of internal pressures. Size: 7cm.
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Agate 121
Square - From £30.40
When there is insufficient material to fill the pocekets in rocks in which agates form the central void may be filled either by quartz or by horizontal bands crystallised from a second infusion of silica - or, as here, a combination of both. Size: 5cm.
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Agate 120
Portrait - From £19.00
When there is insufficient material to fill the pocekets in rocks in which agates form the central void is typically filled either by quartz or, as here, by horizontal bands that crystallised from a second infusion of silica. Size: 6cm.
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Agate 102
Landscape - From £19.00
In this banded agate most of the rock void in which it formed was filled by a later infusion of gel that crystallised as horizontal rather than concentric bands. Various elements are responsible for the colours in agates, but the blazing red and oranges are most likely due - as in artists' pigments - to cobalt.
Original size: 8cm.
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Agate 122
Landscape - From £22.80
When there is insufficient material to fill the pockets in rocks in which agates form, the central void is typically filled either by quartz or by horizontal bands that crystallise from a second infusion of silica - or, as here, by both. Size: 5cm.
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Agate 123
Portrait - From £13.30
When there is insufficient material to fill the pockets in rocks in which agates form the central void is typically filled either by quartz or by horizontal bands that crystallise from a second infusion of silica - or, as here, by both. Size: 7cm.
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Agate 126
Panoramic - From £9.50
This detail is taken from what must be one of the most richly coloured and complexly formed agates in my collection. Essentially a classic concentrically banded agate it appears to have been deformed and fractured both during and after formation. Size: 4cm.
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Agate 125
Square - From £30.40
The basic banding structure of this agate was formed by concentric crystallisation within a void in a rock, but the complexity of many of its details are impossible to explain. Size: 5cm
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Agate 124
Square - From £30.40
The basic banding structure of this agate formed by crystallisation in a void in a rock, but the teeming complexity of many of its details are impossible to explain. Size: 7cm.
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Agate 118
Portrait - From £22.80
This is the centre of a complex agate consisting of concentric bands framing a central void that - one speculates - began to fill with a secondary infusion, forming the lower group of horizontal bands. Quartz crystallised within the remainder of the void, and this in turn frames an area of level-banded agate. Size: 5cm.
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Agate 112
Square - From £30.40
This detail of the perimeter of a banded agate shows part of the 'tube of escape' through which silica was forced under pressure. The central void is mostly filled with quartz, within which a further area of agate, of strikingly contrasting blue and red colours, formed. Size: 3cm.
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Agate 110
Landscape - From £19.00
Agates form in empty pockets in volcanic rocks. Level bands such as this form in a central void left when there is insufficient material from the first infusion of silica to complete the concentric formations characteristic of banded agates. Size: 3cm.
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Agate 113
Portrait - From £15.20
This detail from the perimeter of a banded agate is made memorable by the boldly contrasting colours and the way that the slice happens to cut through the mysterious red feature at an angle, so that its colour is partly exposed and partly seen through translucent material.
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Agate 114
Panoramic - From £11.40
This exquisite detail of an agate was taken from an unmounted cabochon that was probably cut in the late nineteenth century when fashionable ladies would look for promising stones on the beach and have them cut on the seafront for mouting as jewellery back home. Size: 2cm
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Agate 117
Landscape - From £19.00
Most agates form in pockets in volcanic rocks such as basalt, crystallising from a silica gel in concentric bands. When there is insufficient material to fill the rock vesicle, a void is left that may either be filled with quartz or, as here, a secondary infusion of silica that form level bands under the influence of gravity. Size: 5cm.
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Agate 116
Panoramic - From £11.40
Parallel bands like these form in the centres of agates when there is insufficient material to fill the void with bands crystallising roughly concentrically from the surrounding rock inwards. These form later in a central void, and lie horizontally - hence the name 'water-beds' that is sometimes used to describe them. Size: 6cm.
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Agate 115
Panoramic - From £13.30
This agate image is taken from the level-banded centre of a small slice that blends almost seamlessly with the concentric bands that crystallised first. Size: 2cm.
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Agate 128
Panoramic - From £13.30
Even the basic processes of agate crystallisation are disputed by mineralogists, and an extraordinary formation such as this near the perimeter of a banded agate utterly defies explanation.
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Agate 139
Portrait - From £15.20
When there is insufficient material to fill the pockets in the volcanic rocks in which agates form, the central void is typically filled either by quartz or, as here, by horizontal bands that crystallise from a second infusion of silica. Size: 6cm.
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Agate 138
Landscape - From £19.00
Complex formations in banded agates such as these are the result of little understood internal pressures and forces, most likely acting before the bands crystallise from the liquid silica gel that filled the cavity in the rock. Here, the agate bands are interspersed by quartz. Size: 7cm.
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Agate 137
Panoramic - From £9.50
Horizontal formations in concentrically banded agates result from a secondary infusion of liquid silica that fills a void left after crystallisation of bands following the perimeter of the vesicle in rock in which they originate. Size: 6cm.
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Agate 104
Portrait - From £22.80
During agate formation intense pressure can build up, distorting bands prior to crystallisation. A 'dyke' may also form through which liquid gel can be released. This 'folded' formation appears to be the result of a combination of these processes. Size: 4cm.
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Agate 140
Portrait - From £15.20
This detail of a concentrically banded agate appears to show two areas that formed part of an 'escape dyke' through which surplus silica gel was forced under pressure into the surrounding host rock.
Size: 5cm.
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Agate 143
Portrait - From £15.20
A classic agate formed of concentric bands folded around an 'escape dyke' through which material is conjectured to have escaped under pressure. The colours arise from impurities, but the chemical and/or physical processes involved in the band formation is not understood. Size: 9cm.
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Agate 144
Portrait - From £22.80
This detail from the edge of a banded agate shows an 'agate dyke' through which, during crystallisation, surplus silica is thought to escape under pressure into the surrounding rock. Size: 5cm.
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Agate 141
Square - From £30.40
The centre of this agate is filled with a large area of quartz and a level-bedded area of uniformly coloured blue horizontal bands. The purple zone between is animated by small, mysterious formations. Size: 5cm.
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Agate 135
Panoramic - From £13.30
This is a small detail from a large agate slice - the same one as the uncanny 'skull' featured in Agate 134. The basic structure of the concentric bands is clear, but quite what gave rise to the unique details is a matter for speculation. Size: 5cm. |
Agate 130
Square - From £30.40
This is an example of Plasma Agate which is typically transparent to translucent in shades of green and red, with a vein structure in beige to yellow to brown. This specimen comes from California.
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Agate 103
Square - From £30.40
This is a perfect example of agate formation, with the concentric bands completely filling the void. The differentiation between bands is very clear yet delicate, and the subtle blue-grey colour is most likely due to traces of titanium in the original silica-rich gel.
Size: 8cm.
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Agate 129
Portrait - From £15.20
This image is from a specimen from a mine near Parral in the Mexican state of Chihuahua, which was once a busy centre of silver mining. The dark dendritic (leaf-like) formations develop between bands after crystallisation, generally due to inclusions of iron or manganese oxide. Size: 5cm.
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Agate 131
Square - From £30.40
The dendrites that are such a strong feature of this brilliantly coloured Moroccan agate are unusual for their vivid yellow, while the areas between the yellow-fringed red bands are stippled with red dots - very likely the result of hematite. Size: 5cm.
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Agate 132
Portrait - From £15.20
The centre of this image seems to be part of an 'agate dyke' that formed before crystallisation under enormous internal pressures to allow excess liquid silica to escape to the surrounding rock. Size: 5cm.
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Agate 134
Landscape - From £22.80
This is a detail from a large agate slice - the same one as the 'Tibetan landscape' featured in Agate 135. The basic structure of the concentric bands is clear on the left hand side, but the causes of a figure such as this are a matter for speculation.
Size: 8cm. |
Agate 133
Portrait - From £15.20
Banded agates, such as this, form in voids in volcanic rocks such as basalt. In this case the cavity - a tiny one - filled with silica gel and concentric bands crystallised from the perimeter inwards to completely fill the void. Size: 1.5cm.
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Agate 101
Panoramic - From £9.50
Most agates form by the crystallisation of concentric bands of a silica-rich gel that seeps into voids left in volcanic rocks such as basalt. In this example, however, there was insufficient material to fill the void completely, and the hole left in the centre was later filled by horizontal bands from which the images was scanned. Original size: 5cm.
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