OPAL
Specimen opa-18

Dims: 4-1/2" x 4" x 3"

Wt: 2 lbs., 3 oz

Mexico

Although this Opal specimen is not gem-quality, it IS affordable, which is a very reasonable tradeoff. The Opal covers about one-third of the surface area of this specimen, and in some spots is clear enough to see 1/2 inch down into it. Parts of the material are banded, ranging in color from a milky white to brownish orange. All of this rests on an Opalite, or Common Opal matrix. For those who want a large piece of Opal without the large cost, this is a viable option!

Dims: 4-1/4" x 4-1/2" x 2-1/2"

Wt: 1 lb., 4 oz

Chihuahua, Mexico

Though not possessing any of the irridescence, or "fire" that would make this opal worthy of a jeweler's work, it is a very large specimen with a very beautiful "quirk" to it. What makes this specimen so attractive is the incredible amount of internal fracturing(gemologists and lapidarists might call it "crazing") that the stone contains. This particular specimen is made up mostly of opal, and I can't find an area larger than 1 square inch on it that is free from fracturing. Even with all of this "damage," the specimen is not crumbly, and feels solid.

Dims: 1-1/2" x 1" x 1/2"

Wt: 13.2 g

"outback" area, Queensland, Australia

Finally, some opal with the irridescence that makes it so pretty and valuable! This Aussie piece is composed of a flat, tabular chunk of brown, layered matrix, with precious opal on 2 of the thinner sides. Both precious areas display a blue-violet "glow", and have noticeable green flash. These "precious" areas have been coated with a glaze, not only to give them some "shine", but also to help seal in the color-producing microsphericles of water that is present.

Dims: 2" x 1-3/8" x 1-1/4"

Wt: 2.08 oz

"outback" area, Queensland, Australia

This Opal specimen has one large, flat sheet of colorful precious opal on a hunk of brown, banded matrix that seems to house 3 or 4 more incomplete layers of the silica gel. There is a pervasive blue-violet-to-green glow, and several instances of multi-colored flashes of iridescence, or "fire"(people often call precious opal "fire opal," which is an orange-red variety that is mostly found in Mexico). The specimen is mostly coated/saturated with a glaze to preserve the opal, and give it "shine".

Dims: 1-5/8" x 1" x 1-1/8"

Wt: 1.2 oz

"outback" area, Queensland, Australia

Though having a small amount of visible precious Opal, this specimen more than makes up for it with the intensity of the iridescence that the Opal has! Broad blue and green flash fire dominate the exposed gemstone, and some points of bright red are clearly visible. There is other exposed Opal on the piece that does not have such intense irridescence, but the color that is visible makes it all worthwhile! It is all glazed.

Dims: 2" x 1-7/8" x 1-3/8"

Wt: 4.2 oz

"outback" area, Queensland, Australia

This particular opal specimen contains a rather large amount of Opal with no flash fire iridescence. However, it does have a gentle purple glow that pervades most of the silica gel, and there are many gentle, subtle, veil-like inclusions that are very beautiful and actually kind of relaxing to look at! They have been glazed over for protection and shine.

Dims: 3-1/8" x 2-1/4" x 1-1/2"

Wt: 5.4 oz

"outback" area, Queensland, Australia

This chunk of the "land down under" has a somewhat large surface area of precious Opal with no flash fire, but a lovely purple glow that forms a band. The Opal itself fades from a milky translucent to transparent, and covers 3 square inches or so of the brown banded matrix, and is glazed for protective and cosmetic purposes.

Dims: 1.7" x 1.5" x 1.0" (4.3 x 3.8 x 2.5 cm)

Wt: 1.67 oz. (47.4 g)

Lightning Ridge, Australia

This Opal specimen consists of a partially-ground chunk of "Lightning Ridge Knobby" Opal, a well-known variety of Black Opal that often produces very valuable stones. This particular specimen has none of the iridescence, or "fire" that makes Opal such a valuable stone. It does, however, give the average person an idea as to what exactly Black Opal is, as most people that I have spoken with do not know. It consists of a nodule of Opal, part of which has been ground to a smooth, slightly curved face. The matrix ranges in color from a moderate gray to a black coloration (the matrix color of an opal determines whether it is white or black, not the iridescence color) and is generally opaque, though there are spots on the stone that show translucence, and even some transparence. I thought that there may be some "fire" further in the nodule when I first saw it, but some rather knowledgeable opal cutters that I know said that there probably wasn't. A small amount of a hard, shale-like substance fills some of the crevices and hollows in the specimen, acting as a host rock. The smoothed face shows a small amount of "crazing", small, intersecting cracks in the stone that occur if it is exposed to warm temperatures for a long time.

Dims: 4.5" x 4.4" x 3.9" (11.4 x 11.2 x 9.9 cm)

Wt: 3 lbs., 4.6 oz. (1.491 kg)

Chihuahua, Mexico

Part of a very large Opalite nodule makes up this Opal specimen. Opalite is a name that is sometimes given to common opal that is not translucent and has no iridescence. The outer surface of this piece has a definite botryoidal form, showing smooth and undulating shape. There is substantial damage to this surface, as the opal is rather crumbly. The breakage surface of this half of the nodule shows a thin, elliptical patch of precious opal that appears to extend rather deeply into the material. It shows no iridescence, but is transparent and rather clear, though a bit milky. I don't know exactly how deep this vein penetrates the nodule, but it seems to go in at least 1- 2" (2.5- 5 cm).

Dims: 4.2" x 3.0" x 1.7" (10.7 x 7.6 x 4.3 cm)

Wt: 7.59 oz. (215.2 g)

Coober Pedy(?), Australia

Though I am unsure of the exact locality of this specimen, I do know that it is Australian in origin, probably from Coober Pedy, but possibly from Mintabie. It consists of a section of a layer or crust of Opal that was likely partially exposed to the elements. It is definitely precious Opal, though, as it has a milky-white color and shows considerable iridescence or "fire". Most of this is in the form of "pin-fire", which means that the iridescence occurs in little tiny points of coloration. A cross-section of the piece shows that the pin-fire is in a thick layer, looking like very fine, colorful needles from the side. There are at least three discernable layers visible in the cross-section, and they all show evidence of iridescence. One of these layers shows broader flashes of fire, and there is even a purple glow in one spot. Green, blue, red, violet, and yellow colors are all visible in various areas. All of this is best seen under a bright light, though it is partially visible under normal lighting conditions. The specimen is moderately translucent and has conchoidal textures to most of its surfaces, showing a vitreous luster. One side of the piece is noticeably weathered, and appears to represent part the Opal's natural surface. It is a magnificent piece, and one of the largest that I have seen outside of the Tucson shows.

Dims: 1.4" x 0.8" x 0.3" (3.6 x 2.0 x 0.8 cm)

Wt: 8.4 g

Andamooka, Australia

I was told when I bought the material from which this stone came that it is not naturally black- it started out as white opal that was treated with a solution of boiling water, sugar, and sulfuric acid. Nonetheless, the material still produced this magnificent piece, which I only recently finished polishing. It has a dark matrix color of course, and an irregular, uncalibrated shape. It is thicker at one end than at the other, ranging from 0.3- 0.2" (8-5 mm), and a few of the corners are not very well polished. The stone itself does not take a high polish, though it is glossy. It is double-sided, however, so that both sides can be used in a pendant or other jewelry item. One side shows substantial flashes of color-play with predominant green, yellow-orange, and blue-violet colors. The other side, however, has one broad flash of color that blankets about 75% of its surface area. The flash ranges from green to yellow to orange, and then fades to a somewhat dull red glow. It is some of the finest color-play in an opal that I have worked. I think that a pendant would be the best medium for working this stone into jewelry, to take advantage of its double-sidedness.

Dims: 1.4" x 0.8" x 0.3" (3.6 x 2.0 x 0.8 cm)

Wt: 8.4 g

Australia

Though incomplete and showing considerable damage, I think that this is one of the more interesting Opal specimens that I have seen. It consists of most of a clam, with both shells set against each other so that the clam is "closed". These shells have undergone fossilization, and have thus been opalized. All of the clam's outer edge and a portion of one of its other sides is missing; however, this enables one to clearly see the glowing, purple iridescence that one of the shells possesses. The curved striations that line the surface of each shell are heavily worn, but still visible in some places. There is a depression between the shells along the clam's outer edge that is packed with a soft silt. I am tempted to do a bit of careful work with a pick to remove this silt and see how hollow the clam is.

Dims: 2.8" x 2.4" x 0.3" (7.1 x 6.1 x 0.8 cm)

Wt: 1.42 oz. (40.4 g)

Mintabie, Australia

This specimen consists of a thin layer of opal which covers one side of a flat, thin slab of a white, grainy, soft host rock. The opal is not more than 3 mm thick at any point, and is transparent and clear enough to see the host rock underneath. It is very colorful, with flashes of all colors visible depending on the angle of view. This layer of Opal is polished to a high gloss and is heavily cracked, though the material does not show any "crazing". A small piece near the center of the specimen has been chipped out, but the rest of the material is secure. I would not suggest trying to cut this piece into smaller portions, but one could make a large medallion or a brooch with some careful metalsmithing or wire work.

Dims: 1.9" x 0.9" x 0.4" (4.8 x 2.3 x 1.0 cm)

Wt: 18.7 g

Mintabie, Australia

This small specimen consists of a thin layer of white precious Opal that is heavily cracked but held together by what appears to be a thick, cream-colored sandstone base. The Opal layer is polished to a moderate sheen and shows considerable iridescence in a variety of colors. Its base coloration is faintly milky, and it is dimly to moderately transparent, so that one can see through it to the base rock in some spots. Due to the cracks in it, I would not advise trying to make the stone thinner than half its present depth.

Dims: 2.1" x 1.6" x 1.4" (5.3 x 4.1 x 3.6 cm)

Wt: 2.31 oz. (65.5 g)

Krasno, Russia

This odd specimen consists of a crust of reniform Opal that partly coats one face of a formless host rock that looks like it is made of lava. It is of a variety called Hyalite that is commonly colorless and transparent. There is some noticeable damage to the crust, as part of it is missing. The Hyalite has wonderful, rounded formations (see the close-up image), is exceptionally clear, and has a bright vitreous luster. There are a few cracks running through the crust, but these likely occurred prior to the specimen's mining, as they have small amounts of rust trapped within. The host rock has a pale brown color due to weathering on its originally exposed surfaces, but fresh breakage underneath shows a black color, a dull luster, and a very porous nature.

Dims: 1.2 x 0.9 x 0.6" (3.0 x 2.3 x 1.5 cm)

Wt: 7.2 g

Andamooka, Australia

This small thumbnail specimen consists of a partly-sawn nodule of treate black Opal. This material started out as white Opal which was darkened by boiling it in a solution of sugar and sulfuric aci. It has the standard dark gray-black color and pearly-to-vitreous luster and shows only a small amount of translucence along one edge. There is a substantial amount of green and blue-green iridescence visible in the Opal, but the stone is rather dirty, with dust and grime cemented along its convex edges. There is also a substantal amount of a grainy brown matrix rock present, but the specimen is mostly opal by weight. The Opal is wet in both image, so as to take advantage of its iridescence. However, the surfaces that are not sawn have a rather shiny natural luster.

Dims: 1.2 x 1.2 x 0.3" (3.0 x 3.0 x 0.8 cm)

Wt: 5.9 g

Andamooka, Australia

This small specimen consists of a partly-cut and partly-ground piece of Amdamooka treated black Opal. The Opal was originally white, but was darkened in a boiling solution of sugar and sulfuric acid. Thus, its matrix color is a dark brownish-black. It has a dull waxy luster on its uncut surfaces, and a matte luster on its cut ones. When wet, as in the images, its beautiful, colorful iridescence is easily visible, containing colors that span the visible spectrum. Though the piece is rather thin, it is still thoroughly opaque. There are a few bits of a grainy rock embedded in the opal. One could easily lacquer this specimen to give it a permanent "wet look".

Dims: 2.1 x 1.7 x 0.7" (5.3 x 4.3 x 1.8 cm)

Wt: 1.23 oz. (34.9 g)

San Juan del Rio, Mexico

This large thumbnail specimen consists of a few nodules of "Fire Opal" in an opalite matrix. These nodules do not exceed 0.5" (1.3 cm) in diameter, and most are dull and at least partly eroded. One, however, is complete and made up of colorless opal. It shows beautiful and colorful iridescence- it is predominantly blue and green in coloration, but some yellow and red hues are visible.

Dims: 1.4 x 1.3 x 1.1" (3.6 x 3.3 x 2.5 cm)

Wt: 28.1 g

San Juan del Rio, Mexico

The pitted opalite matrix of this specimen contains a few nodules of opal, but only one of these has not been badly weathered. It is also the only nodule that is made up of precious opal, and is exposed by a break on one side. The material shows no discernable form and is colorless, transparent, and quite clear. However, several colorful flashes of iridescence are evident when it is examined- these colors span the visible spectrum, though green and violet are predominant. Two small cracks permeate the material.

Dims: 1.7 x 1.6 x 0.8" (4.3 x 4.1 x 2.0 cm)

Wt: 16.7 g

San Juan Del Rio, Mexico

Three discernable Opal nodules rest in the opalite matrix of this specimen. The largest of these nodules measures nearly 0.5" (1.3 cm) in diameter, and like the others, is incomplete due to partial breakage. These nodules contain a small amount of precious opal that shows no visible crystal form and has color ranging from a rust-red to a milky colorlessness. Though most of the material is dimly transparent, one can see a few flashes of iridescent color inside- green is predominant, but some red is also visible.

Dims: 3.5 x 2.6 x 2.3" (8.8 x 6.6 x 5.8 cm)

Wt: 10.7 oz. (302 g)

Opal Butte, Heppner, Morrow County, Oregon, U.S.A.

This large hand specimen consists of a chunk of "jelly Opal", which is noticeably transparent and clear, resting on a base of common "potch" Opal. The jelly Opal shows no crystal form, but has a natural "outer surface" that is smooth and undulating. It ranges in color from a slightly milky colorlessness to a deep yellow and is essentially transparent, though being opal, it shows the standard turbidity. Where fractured, it shows the standard conchoidal curvature and a vitreous luster, but its natural faces show a duller, pearly luster. I have not seen a piece of opal quite like this one before.

Dims: 2.1 x 1.3 x 0.9" (5.3 x 3.3 x 2.3 cm)

Wt: 1.15 oz. (32.8 g)

San Juan Del Rio, Mexico

The opalite host rock of this hand specimen contains several partial Opal nodules. These Opal chunks show no form, of course, and all but one have been broken. The opal is colorless, transparent and quite clear, but shows the faint, milky turbidity that is known as opalescence. Colorful green, blue and red iridescent "fire" is visible in a few of them.

Dims: 2.6 x 1.7 x 1.3" (6.6 x 4.3 x 3.3 cm)

Wt: 1.79 oz. (50.7 g)

San Juan del Rio, Mexico

This hand specimen consists mostly of Opal, but most of it is common Opal, which is sometimes called "potch". There are, however, a few layers and rounded nodules of jelly Opal. These nodules are transparent and moderately clear, showing the slightly cloudy "opalescence" that is a hallmark. Its color ranges from colorlessness to the moderately deep orange of fire opal, and the largest nodule contains some subtle iridescence in one area. The common Opal has a deep red-brown color and is essentially opaque, and has been lacquered.

Dims: 1.4 x 0.9 x 0.6" (3.6 x 2.4 x 1.5 cm)

Wt: 8.5 g

Andamooka, Australia

This large thumbnail specmien consists of an amorphous chunk of white precious Opal. It shows no crystal form and exhibits the standard conchoidal fracture and dull vitreous luster. Though it generally has a white color, several bands of colorful iridescence are present, along with a small amount of rough, dull matrix rock. Cutting a stone from this piece is possible, but the colors show rather well just as it is. In order to prevent crazing (the cracking of an opal's surface), it is best to store it in a moist environment and guard it against extreme changes in temperature.

Dims: 1.0 x 0.9 x 0.4" (2.6 x 2.4 x 1.1 cm)

Wt: 6.6 g

Andamooka, Australia

A shapeless chunk of precious white Opal comprises this thumbnail specimen. It exhibits conchoidal fracturing and a dull vitreous luster, and is translucent. Though the material is white in color, it also exhibits a beautiful, multicolored iridescence. One side of the piece is covered with a thin crust of a dull host material. Such a piece could be cut with care into an attractive gem.

Dims: 1.3 x 0.9 x 0.3" (3.3 x 2.2 x 0.7 cm)

Wt: 5.2 g

Andamooka, Australia

This flat Opal piece is partly encrusted with a thin layer of matrix rock. However, much of its surface is fractured, showing a dull vitreous luster and the standard white color of the material. Portions show a colorful iridescence that occurs in layers within the stone- these layers are rather badly skewed, so most of the material would be wasted if one were to try to cut it into a gem.

Dims: 1.0 x 0.6 x 0.4" (2.6 x 1.5 x 1.1 cm)

Wt: 3.7 g

Andamooka, Australia

This small chunk of white precious Opal shows definite layerings of iridescent color between layers of darker, almost gray Opal. It shows conchoidal fracturing, a dull vitreous luster, and translucence. Two large cracks would make it difficult at best to try to cut a stone, and one area is covered with a thin layer of a dull host rock.

Dims: 1.9 x 1.6 x 1.1" (4.8 x 4.2 x 2.8 cm)

Wt: 2.0 oz. (58 g)

yowah opal field, Queensland, Australia

This lovely specimen consists of the two halves of a split "Yowah Nut" Opal. The halves show several concentric outer layers of rust-stained jasper and "potch" opal that surround a core of precious opal. Being opal, there is no crystal form, and the precious material shows a conchoidal fracture and vitreous luster. It is transparent and clear, but contains many "potch" inclusions. This precious material also shows beautiful blue and green iridescence, some of which is obviously layered.

Dims: 1.6 x 1.3 x 0.8" (3.9 x 3.2 x 2.1 cm)

Wt: 19 g

White Cliffs, New South Wales, Australia

A shapeless chunk of precious white Opal makes up this small hand specimen. It shows no evidence of any crystal form, and all faces are conchoidal and exhibit a bright pearly luster. The matrix has the standard milky-white color, and several parallel layers within exhibit the classic colorful iridescence of Opal. There is no host material present.

Dims: 1.3 x 0.9 x 0.6" (3.3 x 2.4 x 1.6 cm)

Wt: 18 g tot. wt

Yowah opal field, Queensland, Australia

(2 pcs.) This small thumbnail piece consists of the two broken halves of a Yowah nut Opal, which is basically an opal in the center of a concretion. The Opal shows no crystal form, of course, and has the conchoidal curvature and vitreous luster that are standard. It is transparent and shows a beautiful blue iridescence. The surrounding concretion is made up of "potch" or common opal that has a rusty-brown color and a dull waxy luster- its outer surface is weathered and completely dull.

Dims: 5.8x3.3x2.5" (14.8x8.4x6.3 cm)

Wt: 13.9 oz. (392g)

Chalk Mountain, Spruce Pine, North Carolina, USA

This rather ugly rock is a sample of hyalite, a flourescent variety of opal. The rock is porous and not very pure (there are several minerals present), but under a loupe the hyalite resolves into thousands of intergrown balls of hyalite, which appear translucent to nearly transparent, and also exhibit a most unusual melted-wax luster, somewhat reminiscent of smithsonite (you need a loupe to see this). The opal also has a very bright green flourescence under short-wave ultraviolet (the image does not do it justice).

Dims: 3.6x1.8x0.9" (9.1x4.7x2.3 cm)

Wt: 2.66 oz. (75.2g)

Mintabie, Australia

This is a very pretty and colorful hand specimen of opal from south Australia. It is a thin (1 to 2 mm) thick layer of opal on a sandstone matrix. The opal has been polished, and while it is mostly green, there are zones of blue and even purple opalescence Overall, this is an excellent opal specimen for a collector, as there is a lot of colorful opal and it displays well.

Dims: 2.6x2.4x1.2" (6.5x6.0x3.0cm)

Wt: 3.8 oz. (107g)

Mintabie, Australia

This chunk of sandstone from southern Australia has one surface coated with a thin layer of excellent opal. While very thin (less than 1mm), it shows excellent color, reflecting all of the colors of the rainbow. Each of the areas of opal tends to have a small range of colors, mostly green, yellow, and orange, but there are some small areas of deep red, purple, and blue.

Dims: 2.2x2.2x1.7" (5.6x5.7x4.3cm)

Wt: 4.96 oz. (140.3g)

?

This opal specimen has an excellent violet color, and a somewhat unusual appearance. The host rock is brown and nondescript. The opal is, I believe, filling the cracks and surrounding what may have been a fossil plant of some sort. There is a pattern of vesicals which looks a bit like some dried weeds (internally), and this plant could have been opalized, and then the remaining cells could have disolved away. Lending evidence to my theory is a second area which does look like fossilized plant material (from the outside), with highlights of violet opal along its edge and penetrating transverse cracks in the wood. There are numerous bits and veins of the opal scattered on the matrix.

Dims: 1.61x0.91x0.28" (4.1x2.3x0.7cm)

Wt: 0.29oz. (8.2g)

Quilpie, Queensland, Australia

This boulder opal specimen has a good amount of color (greenish-blue), although its fire is limited to a narrow band across one end, and a little bit near the point. The thickness of the opal varies from nearly 0.5mm at the end with the fire, to barely perceptible at the other end.

Dims: 1.42x1.34x1.10" (3.6x3.4x2.8cm)

Wt: 0.92oz (26.0g)

Lightning Ridge, Australia

A stream tumbled nodule of opal has been partially polished to reveal the pretty violet opalescence of the stone. The overall shape is quite irregular, due to the softer matrix having been largely eroded away. There are patches of color on all sides of this specimen, although most is on the partially polished side. This is one of those specimens that looks best wet, as more of the opal is visible when the surface is smoothed by wetting.

Dims: 1.10x0.94x0.82" (2.79x2.39x2.09cm)

Wt: 50.4ct or 0.36oz. (10.08g)

Lightning Ridge, Australia

This thumb-size nodule of opal has been polished on one surface to highlight its intense opalescence in purples, blues, and greens. The best color is limited to about 1/3 of that surface, although spots of color are visible on several sides. The image does not do this justice, as the variety and play of colors is not captured by my camera.

Dims: 1.35x0.84x0.47" (3.42x2.14x1.20cm)

Wt: 0.28oz (7.88g)

Lightning Ridge, Australia

This is one end of a Lightning Ridge opal that was cut off of a larger piece and polished to reveal its excellent transparency and color. The nodule has an opaque white coating over most of its surface, although there are some fractures offering windows to the opal (and some color) within. The opal is transparent but somewhat smoky in color, and has black, wispy inclusions. The opalescence is nearly everwhere, and is a bright purple (the image shows blue, but this is due to my camera). This is a very nice opal, indeed.

Dims: 1.50x1.38x0.46" (3.80x3.50x1.16cm)

Wt: 0.67oz (19.1g)

Mintabie, South Australia

A flat piece of a white host rock has a 1.5mm thick layer of opal.. This opal has a lot of fire, as little colorful sparkles in all of the colors of the rainbow. It also has a network of fine cracks. The opal has a nearly uniform milky translucence, and the fire comes from throughout the material.

Dims: 5.10x3.67x2.29" (12.96x9.32x5.82cm)

Wt: 11.04oz (313g)

Chalk Mountain, Spruce Pine, North Carolina, USA

This is a porous intergrowth of very white, translucent hyalite blobs (a variety of opal). Most of the specimen is hyalite, although there is a coating on the back that is an opaque white mineral, plus the back has several areas of some dark rock. The specimen is rather porous, and some of the hyalite is transparent. Still, the specimen is not very interesting unless it is exposed to ultra-violet light, then it glows a very bright green. The opaque mineral on the back also glows a barely perceptible pink, just enough to make me believe that it is calcite.

dims mm=27.24x11.93x6.81

wt g=3.9

Mintabie, South Australia

This relatively thick opal specimen has good color over most of the polished surface. While it displays nearly every color in the rainbow, they are relatively faint.