Stones by zodiac signs

How to distinguish Ethiopian opal from Australian?

This article will debunk a couple of myths about opals that exist in modern society

Consider some types of opal and find out how to distinguish natural opal from other identical stones and minerals. At the same time, we will not speculate on beautiful pictures of sparkling and iridescent noble (let us not confuse them with fire) opals, which is what other sources usually do.

So, the first myth about opals

For some reason, everyone thinks that opal must play with all its colors and shimmer with the entire spectrum of colors, like a mosaic in a kaleidoscope. But in reality this is far from the case. Natural opal – This is practically the only mineral that does not have a crystal lattice. Opal consists of globules, microspheres of silica, which bind together a small amount of water (4-12%). In nature, there are 130 (one hundred thirty!) types of opal, of which only no more than 5-6 types of opals shimmer with colors. The rest have a single color, may even be a dirty gray color and even completely opaque. That is why, when saying the word “opal,” you need to clarify what exactly you are talking about. By the way, in search engines, when you enter the word “opal”, a million pictures pop up and we only see precious opal. Well, therefore, it becomes clear why people associate opal with the play of color. If so, then let’s start with it. There is a lot of information on the Internet about the very nature of opal play. We will only dwell on the types of noble opal and how exactly to distinguish them from a fake. By nature natural opal – petrified silicon gel. At the stage of its formation, opal is able to permeate porous sedimentary rocks – this is how they grow Honduran black opals и Australian andamooka opals — bituminous sandstones. Or it can fill cracks in ferruginous rocks – this Australian boulder opals. The color scheme of the game of opals can include 1, 2 or 3 colors – harlequin opal. In this case, the size of color fragments can vary from 1 mm to the entire plane of the stone. The matrix of a solid opal (the body of the stone) can be black: Australian opals from the mine Lightning Ridge, either chocolate or white: Ethiopian opals. The most expensive are full spectrum black opals, Australia, Lightning Ridge.

The second myth about opals

The main confusion begins when it is discussed black opal. But this is where no one needs to worry – black opals are not imported into our country for two reasons. Firstly, due to the very small volume of opal mining. After all, only Lightning Ridge – the indication of this particular place is a guarantee of real black opal. Well, and the price, of course, too. The price for it is not just high, but astronomical, even for our domestic oligarchs. And if it’s light Ethiopian opal costs on the modern market $50 per carat for a 7 mm stone, then natural black opal depending on the number of colors and blackness of the matrix, it can already cost 1-5 thousand dollars per carat. This means that a stone identical in size will cost not 2-3 thousand rubles, but 60-300 thousand. “What is it then that the pages of online stores of products with black opal are full of?” – the attentive reader will exclaim. And everything is very simple. There is a technology for so-called smoking of ordinary light, inexpensive opals – this is carbon saturation. And what gives away such “smoked” opals is the price – they are sold at the same price as light ones. And what is called black, they are quite arbitrary. Pricing for Precious opals are a rather complicated topic. You often see carefully sorted rough stones from Ethiopian opal traders. Prices start at 2 euros per gram, and just a couple of years ago they could be bought for 0,5-1 euros. 2. Today there are a lot of inexpensive imitations of precious opal. Distinguish precious opals from fakes externally, without skills or specialized equipment, you can turn the stone in a circle and watch the play of colors. First: first of all, the sparkling fragments should not have clear boundaries, and second: when turning, these spots seem to fade away and others light up, gradually smoothly turning into each other and changing colors and shades. If the insert or bead is made entirely of opal, then it is most likely Ethiopian. Ethiopia today occupies 90% of the entire opal market in terms of all sales volumes, and therefore itself has greatly reduced the price for them. Australian opals they usually represent a thin layer of opal on a matrix (parent rock). Very widespread opal doublet и triplet opals, mostly Australian, is when a thin layer of opal is glued onto a dark layer of foreign stone. In a triplet, a transparent colorless plate of either rock crystal or moonstone, but most often synthetic, is glued on top, which makes such an opal reliably protected and almost eternal. But, as you understand, the opal in such an insert is not even half and such stones, of course, are not measured in carats. You can even see mosaic triplets – this is when the middle layer consists of a mosaic of 1-2 mm thin plates of noble opal. And depending on the skillful selection of such a mosaic, a cabochon with dimensions of 10×7 mm can cost from 3 to 10 dollars. And all this is very much abbreviated information about precious opals.

And now the non-iridescent opals

In general, the concept of opalescence relates specifically to translucent and plain opals and means a significant dispersion of light, like a cloud, a cloud. As we study, let’s learn how to distinguish opals. The most important thing here is to find the chip. For example, in beads you need to look through a magnifying glass at the mouth of the bead itself. On opal fragments, everything is clearly visible at once. On a cabochon you also need to look at the girdle with a magnifying glass. Natural opals always have a unique oily sheen on the chip, like melted butter. And the more water the opal contains, the more oily its shine, as if after a good polishing. The chipping of more durable low-water opals looks like frozen oil. Next, the next one is fire opal. Absolutely translucent to transparent plain natural opals Color ranges from yellow to brown-orange. The most classic ones are orange-carrot ones. And there is absolutely no play in them, no dispersion, by the way, and no shimmer or shine with all the colors. These natural opals Our market is supplied by Mexico – more expensive and rich ones, and Brazil – mainly light and inexpensive opals. Beautiful natural fire opals once mined at the Voznesensk field in Kazakhstan. But the old days have passed and now opals are no longer dug there, but amateurs pick them. White opal и blue natural opal They are usually inexpensive, but they are not very common now. Instead of them, for some reason, imitated and artificial opal. The exception is their varieties: andopal – greenish-blue Peruvian opal and hyalite is a colorless opal. One must take into account the luxurious Kazakh dendroopal. Just 20 years ago there were quite a lot of them on the market. The prefix “dendro” means that along with the opal, branches were crystallized in it – dendrites of manganese oxides. Dendritic opal. Natural green opal, just like chalcedony, is divided into 2 groups depending on the chromophore – nickel, this chrysopal, or chlorine – chloropal, this is wonderful ungvarit and incredible beauty kiwi opal, pistachio opal. Chrysopal often happens in the vicinity of chrysoprase in one block, as, for example, in Kazakhstan at the Pstan deposit. Sometimes it is called something like prazopal. Chloropals are called differently depending on where they are harvested. And let’s finish our study with the famous opal from Peru – Peruvian opal, it is very beautiful and popular natural pink opal. By the way, among all opals it is probably the most relatively inexpensive. Well, we briefly studied main types of opal. Thank you all for your attention. One of the most visually spectacular and unique stones, whose beauty cannot leave anyone indifferent, is, of course, opals. The largest deposits of this stone are located in Australia, Mexico, Ethiopia and Peru.

What is opal and how is it formed?

Opal is a mineraloid that is formed from a solution of silica and water: water seeps through sandstone, picking up tiny particles of silica. Getting into the cavities, water precipitates silica in the form of microscopic spheres, from which opals are subsequently formed: they are deposited at a fairly low temperature and can form in cracks in almost any rock (most often limonite, sandstone, rhyolite, marl and basalt). Opal mineraloid in rock and opal mining If the spheres that make up the mineral are random in location, size and shape, then ordinary opals will be obtained without optical effects, but if the spheres are the same shape, size and neatly stacked on top of each other, they will scatter light, creating precious (jewelry) opals . Precious and non-precious opals

Precious opals and what determines the color of opalescence?

Precious opal is a type of opal that exhibits a phenomenon known as play of color (called opalescence in opals), which occurs as a result of white light passing through a microstructure of orderly silica spheres. When light passes through the spheres and gaps, it diffracts (splits). Like a prism, the opal splits white light into all the colors of the spectrum and the light eventually reflects off the top of the stone, at which point we see the beautiful colors of the opal. Opal is the only known gemstone that refracts light so naturally. The size and angle at which the light is split determines the resulting color: small spheres produce only blue opal (the most common color), while larger spheres produce red (the rarest color). The decomposition of light in precious (Noble) opal, which leads to the effect of opalescence of different colors.

Characteristics of opal

The variety of natural opals is determined by two characteristics: body tone and transparency. Body tone – This refers to the base tone of the stone. The tones of light, dark and black opal range from colorless, white, through various shades of gray to black. Light and dark body tone in opals Transparency – Any opal can be opaque, translucent or transparent. Transparent and opaque opals

Types of opals

Black opals black opal – the most valuable of opals, which is mined mainly in Lightning Ridge, Australia, the “capital” of black opals. Despite the name, opal is not pure black – black opals include all stones with a dark base tone, this type of opal is very rare. White opals К white opals All opals with a base shade ranging from colorless to medium gray are classified as white opals, although technically only stones with a milky body color are considered “white opals.” White opals are more common, although the opalescence is not as noticeable on them. One of the most striking representatives are Ethiopian opals with bright tints of color. Boulder of Opals Boulder opal (“Boulder”) – a type of opal in which part of the stone is the host rock, often there is simply a thin vein of precious opal. Boulder opal fills cracks and voids, usually in ironstone boulders. The color may be dark or light, depending on the appearance of the stone when viewed from the surface. Boulder opal tends to split: when split, 2 halves of opal are left with a naturally polished surface. fire opal Mexican fire opal is a transparent or translucent opal with a warm base color ranging from yellow to orange and red. Often this type of opal does not show any play of color, sometimes showing bright green flashes. Fire opals without play of color have the trade name “jelly opals.” The most famous types of Mexican opals are Cantera opal and Mexican water opal. Mexican opals: fire (top left), jelly (top right), Cantera (bottom left) and water (bottom right) Types of Brazilian and Mexican opals Matrix opals The term matrix opal is usually used where the opal is dispersed within the host rock in which it formed. The veins of matrix opal, iridescent with all the colors of the rainbow, are quite thin, so it is often given an unusual shape during processing in order to achieve maximum play of light. The most popular types are Boulder Matrix Opal from Queensland (which has iron ore as its host rock) and Andamuuka from South Australia (which is often further processed to darken the base colour). Matrix opal from Queensland (left) and Andamuuk (right) Hyalite opals Hyalite or Muller glass Opal is a colorless opal that has a glass-like appearance, but in rare cases it shows a faint tint of color (blue, green or yellow). The two most famous places for this type of opal to grow are Oregon and Mexico (in Mexico it is called water opal). Girasol-opal Girasol opal is a type of hyalite opal that exhibits a bluish glow or luster Peruvian opals Peruvian opal is an opaque blue or pink opal formed from volcanic rock at low temperatures. Unlike other common opals, Peruvian opals lack play of color. You can find two types of Peruvian opal – blue Peruvian opal and pink Peruvian opal. Due to its high water content, Peruvian blue opal has a cool blue hue and is also heat sensitive. Exposing these opals to strong sunlight can cause them to lose brightness and eventually shatter. Pink Peruvian opal boasts a vibrant pink hue and is also found in Western Australia. It is also known by the trade names Andean opal and angel opal. Ethiopian opal Ethiopian opal Another heavyweight in the opal market besides Australia is Ethiopia. Opals with a light body tone with bright iridescence, which were not inferior in quality to Australian ones, but were more affordable, quickly won the hearts of people. Various Ethiopian opals Other special types Harlequin opal – the rarest and most expensive of opal patterns. The play of light in it occurs in geometric inclusions; this is a very rare phenomenon. Crystal opal – any of the opals with a transparent or translucent body tone with a play of light, meaning you can see through the stone. Crystal opal can have a dark or light body tone, leading to the terms “black crystal opal” and “white crystal opal”. Honey opal – a type of opal that is honey-yellow in color, translucent or transparent, resinous to glassy in appearance. It may or may not have a play of color. White synthetic Gilson opal

synthetic opal

All varieties of opals are also synthesized in laboratories. The most popular type of synthetic opal is Gilson opal: the discovery of the ordered spherical structure of precious opal led to its synthesis by Pierre Gilson in 1974. The resulting material differs from natural opal in its regularity; When magnified, the colored spots are seen to be arranged in a “lizard skin” or “chicken wire” pattern. Additionally, synthetic opals do not fluoresce under ultraviolet light. Synthetics also usually have a lower density and are often very porous, although now synthetics are being made more stable – such specimens retain color, transparency, and do not absorb fats and oils. Modern companies have learned to make synthetic opals that are in no way inferior in terms of external qualities or prices; professionals in this market have their own recognizable style, by which the authors of the imitation can be identified. Examples of synthetic opals from one of these companies

Doublets and triplets of opals

Separately, it is worth highlighting doublets and triplets of opals – they are not fake, but composite minerals – these are stones that are obtained by gluing together several layers: • The doublet is made from a layer of natural mineral and a dark stone backing (for example hematite or obsidian)
• The triplet consists of three layers: the substrate, the opal itself and the glass dome on top.

Opal cost

  • weight;
  • colors;
  • pattern;
  • shine;
  • transparency;
  • origin;
  • age;
  • stories

Example of collectibles: Halley’s Comet ($1,2 million), Black Prince, Virgin Rainbow (about a million dollars)

We learned what opal is, what determines its opalescence color, what the characteristics and types of opals are, what doublets and triplets are, and how the cost is formed.

We hope you find this article helpful. It is impossible to fully reveal all the nuances of this multi-layered topic in one article, so if you still have questions, write in the comments, and we will answer.

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