- Varieties of Lapis Lazuli
- Sources of Lapis Lazuli
- Physical & Optical Properties of Lapis Lazuli
- Test and Identification of Lapis Lazuli
- Valuation and Buying Tips for Lapis Lazuli
The lovely blue lapis-lazuli (pronounced LAP-us-LAZ-u) chares with turquoise the distinction of being among the most prized of all gemstones in earlier civilisations. There is little doubt that it was at least as sought after as turquoise and probably even more in demand. At that time there was only one source for it, compared with at least three for turquoise, and that source was remote from the Mediterranean area. Descriptions by Pliny and others leave no doubt that lapis was the sapphire of the ancients. Pliny referred to sapphire and described it in the following un-mistake-able fashion: "Sapphires contains spots like gold. It is also sometimes blue I although sometimes and indeed rarely, blue tinged with purple. It is never transparent. This is certainly no description of sapphire, but fits lapis-lazuli perfectly.
Both in Babylonia and Egypt, lapis was very highly valued. This is shown by the use of the name of poetry and song. In a hymn to the moon god Sin, for example, he is addressed as "the strong bull, great of horns, perfect in form, with long and flowing beard, bright as lapis-lazuli." During this period, the gem was believed to be a cure for melancholy and for the quarter fever, an intermittent fever that returned each third day. It often appeared as an important item in the lists of tribute paid to Egypt and among the gifts sent by Babylonia to the Egyptian monarchs. From this material lamulets, cylinder seals, scarabs and other articles were made, many of which have been recovered from ancient tombs and preserved for us in museums. The Egyptian high priest is said to have worn a lapis image of Mat, the Goddess of Truth, around his neck. At that time the gem was one of the most important of commodities, and trips lasting years were required to travel to the Badakshan mines and return with the precious cargo. In reports of loot brought back from the treasures of vanquished nations by conquering armies, lapis is often mentioned before gold or other precious substances.
From the days of ancient Greece and Rome through the Renaissance, lapis was pulverized to make the durable pigment called ultramarine, which was used extensively to produce the intense blue in many of the world's most famous oil paintings. In more modern times, however, ultramarine was replaced by a synthetic product made by fusing kaolin with sodium carbonate and sulphur. The Greeks and Romans also used powdered lapis as a tonic and purgative. In the Middle Ages, when illuminating manuscripts was a fine art, monks powdered the gem, kneaded it into a dough moistened with beeswax, resin and linseed oil, and used it in the monastery book binderies. However, the pigment was so expensive that it was a mark of wealth to commission a painting that specified the use of it. The ancient Chinese called lapis "dark-blue goldstone". They ground it into a cosmetic for painting their eyebrows and made sheets of it into screens studded with pearls.
Unlike any other important gem, Lapis is actually a rock, rather than a mineral. It is composed primarily of a blue mineral, LAZURITE, plus variable amounts of pyrite and calcite and minor amounts of diopside and other minerals. Unfortunately, there has been a confusion of names applied to the various blue minerals and the lapis rock, some of which have stemmed from the same source. At least a part of the confusion started many centuries ago, and it was compounded several times over. Lapis-lazuli is from the Lat in "lapis" meaning "stone" and "lazuli" meaning "blue" (actually, "lazulus stone"). The root of these words is from an Arabic word "allazward" meaning "heaven", "sky" or simply "blue". Apparently, the French word "azur" came about from the originator's belief that the original root of "lazurius" (a later Latin form) or of the Arabic word was "L'az u lus". In other words, it was thought that the first letter was the article, rather than the first letter, so we have "azure" in English and the mineral azurite. Thus, there are three distinct minerals with names meaning blue: azurite, lazulite and lazurite. But this is not the only source of possible confusion, for there has been a difference of opinion among mineralogists regarding a possibility that lazurite and a second mineral, hauynite, were actually the same mineral formed under slightly different circumstances. Most American mineralogists regard lazurite as a separate and distinct mineral.
Lapis is always opaque to semi-translucent and is usually slightly violetish blue. Sometimes, it is almost bluish Violet, but the blue usually predominates. Specks of golden colored pyrite and white calcite are frequently present. "Swiss lapis" and "German lapis" are misleading terms used to refer to jasper or chalcedony dyed blue by the use an ferric-ferrocyanide, or Prussian blue. Calcite or limestone and even inferior lapis are also sometimes dyed and sold under one of these trade names. The following names are used in the American jewelry trade to refer to various qualities of lapis-lazuli:
Persian LapisThis quality, which is actually from Afghanistan, is the finest color and is difficult to obtain. It is an intense, evenly colored, slightly dark violetish blue with little or no pyrite and no white calcite veining.
Russian, or Siberian, Lapis.This type occurs in various tones and intensities of blue contains pyrite, and is usually of good quality.
Chilean Lapis.Material referred to as Chilean lapis contains numerous white calcite inclusions and is often tinged or spotted with green. It is usually the least valuable type.
Uses of Lapis Lazuli
Lapis-lazuli is usually fashioned into cabochons or flat, polished tablets, but many of these flat pieces are also carved. Beads, clock cases, cigarette boxes and various other ornamental objects are also made. This stone has long been a favorite of the Chinese for carving figurines, snuff boxes, pendants and other small objects. In Russia it is a favorite material for wainscotting. Some precautions are necessary when fashioning lapis. First since it grinds away rapidly, care must be exercised in this operation. Also, close attention must be given to any protruding pyrite inclusions, because the surface may undercut badly. The most satisfactory polish is obtained by using either "Linde A" or chromic oxide on a leather lap.
Lapis-lazuli is usually fashioned into cabochons or flat, polished tablets, but many of these flat pieces are also carved. Beads, clock cases, cigarette boxes and various other ornamental objects are also made. This stone has long been a favorite of the Chinese for carving figurines, snuff boxes, pendants and other small objects. In Russia it is a favorite material for wainscotting.
Some precautions are necessary when fashioning lapis. First since it grinds away rapidly, care must be exercised in this operation. Also, close attention must be given to any protruding pyrite inclusions, because the surface may undercut badly. The most satisfactory polish is obtained by using either "Linde A" or chromic oxide on a leather lap.
The usual means by which lapis is formed is by the alteration of an impure limestone by the "cooking" effect caused by an intrusion of an igneous mass nearby. Thus it may be regarded as a product of contact metamorphism.
Throughout the recorded use of lapis the principal source has not been Persia, as the trade name would suggest it but near Firgamu, on the upper part of the Kokcha River, a tributary of the Oxua, in the Badakshan district of Afghanistan. Here it occurs in strata of black-and-white limestone. Both ruby and spinel have been found in the same region. A Siberian deposit is located at the southern end of Lake Baikal, where it occurs in a dolomitic limestone. A newer Russian source of material, similar to that in Badakshan, has been reported near Khorog, in the Pamir Mountains.
The only other important locality is the Ovalle Cordillera (Andes Mountains), Coquimbo Province, Chile. Material from the Ovalle deposits was used for decorative purposes by the Incas; one of the largest masses of lapis ever recorded, measuring 24 x 12 x 8 inches, was found in a Peruvian grave. Another Chilean deposit, but of less significance, is situated farther north, near Antofagasta. Other localities of minor importance include the Dattaw Valley near Mogok, Upper Burmal; Italian Mountain (Sawatch Range), Gunnison County, Colorado; Cascade Canyon, San Bernardino County, California; and Mono Lake, Mono County, California.
Since the Badakshan deposits have been worked for approximately six thousand years, they have been mentioned frequently in history. It is known, for example, that Alexander the Great visited the Oxus River Valley three hundred years before Chirst and that his army was instrumental in spreading the knowledge of lapis to the West. It is also recorded that Marco Polo passed through the region of 1271 and praised the beauty of this blue gem. But there was little real knowledge of Badakshan in the West until the nineteenth century, when several Englishmen and a Persian surveyor explored the area and provided the first accurate information of modern times. Later, in 1870, a long English adventurer had the courage and curiosity to go into the then all but forgotten Badakshan mountains to discover the exact nature of the ancient mines. On horseback he crossed the deep marshes of the valley, then entered a pass and climbed a high ridge that cuts off the upper valleys. From here he followed the Kokcha, which is a Turkish word meaning "blue river". A narrow, twisting trail, made dangerous by landslides, led to the mines. At times, when the route became too difficult for his horse, he would be forced to continue on foot, using crude leather busking to protect his feet and a heavy walking stick to help him across the many deep chasms. The valley closed in on either side with high naked mountains. The path became so steep and dangerous that the traveler then began to understand the warning that had been given him by a native mountaineer before the journey: "If you wish not to go to destruction, avoid this narrow valley." Curving lines of black-and-white limestone marked the mountain in which the mine shaft opened. A little way inside, the explorer found a large hole where the roof had collapsed. In some places the galleries were so blocked with debris that it was necessary to crawl on hands and knees. Accidents had been frequent and parts of the mine were named for workers who had lost their lives there. In the face of bitter wind, he set out to investigate another mine. He passed native travelers who wore masks of horsehair to protect their eyes from the glare of the snow. The wind blew so hard that he was forced to dismount. But more than the gale soon stopped him: avalanches and crumbling ice made the road impassable. Reluctantly, and without seeing so much as one piece of lapis, he was forced to turn back.
There has always been a tendency for writers (in fact, most of us) to romanticize the gem deposits of the world. Many of the most important are located in what we of the West (Europe and the Americas) often refer to as the "mysterious East". If inaccessibility is an index of romance and mystery, it would be difficult to imagine a better example than the important lapis deposits of the world. Even Kabul, the capital city of Afghanistan, is very rarely visited by outsiders, but it is a crossroads compared to the remainder of the country. And even by Afghanistan standards, the location of the lapis mines must be considered remote. Most of the country is ruggedly mountainous. The central range of the northeastern portion, the mighty Hindu Kush, has peaks of 24,000 feet. Although the lapis mines are in the northeastern corner of Afghanistan, they are north of the main Hindu Kush range. The Oxus River (or "Amu Darya" as the Russians know it) forms the boundary between the Soviet Union and northeastern Afghanistan before turning north into Russia. The Pamir Mountains, which lie in both countries, are drained by the headwaters of the Oxus. The Kokcha has its headwaters in the Hindu Kush. To reach the mine site requires days on horseback after leaving the last city to the north, followed by a climb of some 1000 to 1500 feet up the precipitous side of the steep-walled valley of the upper reaches of the Kokcha. In view of these problems, it is not difficult to understand the dearth of eye-witness reports, of activities at the mines.
This much may be concluded from reasonable evidence: the mines have been worked only sporadically throughout much of their history. They appear to remain productive, but are apparently worked only by or for the government. Recent efforts by colored-stone dealers to obtain lapis in quantity have met with offers of government-regarded and government-stored lots held at high prices. It was indicated to these dealers that stocks of the finer qualities were adequate to meet any anticipated demand. Apparently, the inaccessibility of the mines precludes bringing out anything less than the more expensive grades.
Today, mining is reportedly carried on in the same way and under the same rigorous conditions as it was centuries ago. The method consisted of building a fire on the gem-bearing rocks and then causing them to crack by the application of cold water. The sheets of lapis were then pried out with little difficulty. The operations were usually accomplished during the winter, probably because that was the only time water was readily available (in the form of snow) high on the valley walls. There was a time when the workers were supposed to believe that if the mines were approached in summer, huge, venomous reptiles would rush out and devour them. This belief may be held by many in Badakshan even today. Since the mines seem to be under the control of the government at present, it is possible that blasting, followed by drilling, is the mining method used today. However, since the area is too remote for air compressors, drilling is probably done only by hand tools.
|Chemical Composition||Lazurite is a mineral in the sodalite group: it is common for two or more of the minerals of this group to be represented in the same rock. A glance at their formulae will show they are very similar chemically, and, as might be expected, very similar structurally. Lazurite, however, constitutes the bulk of lapis-lazuli. The chemical formula of lazurite may be expressed as (Na,Ca)8[(S,Cl,SO4,OH)2|(Al6Si6O24)]. The sodium is often replaced in part by potassium and the solphur by S04, chlorine or selenium. Hauynite may be given as (Na,Ca)4-8Al6Si6(O,S)24(SO4,Cl)1-2and sodalite as (Na4Al3(SiO4)3Cl) .|
|Crystallographic Character||Cubic. Gem material is in the form of a granular aggregate|
|Hardness||5 to 6. The variation is related to the amount of impurities present.|
|Specific Gravity||2.50 to 3.0; normal, 2.75. The higher S. G.s are caused by excessive amounts of included pyrite.|
|Streak||White to light blue|
|Characteristic Inclusions||Brassy-yellow pyrite and white calcite.|
|Degree of Transparency||Opaque to semi-translucent,|
|Luster||Polished surfaces are vitreous to waxy; fractured surface are dull.|
|Birefringence||Strong, but not apparent by any gemological test.|
|X-Ray Fluorescence||Very weak to none. The calcite inclusions, however, may fluoresce brightly I creating a mottled effect.|
|Transparency to X-Rays||Transparent.|
|Ultraviolet Fluorescence||The calcite inclusions fluoresce moderately in a pink color under long wavelength. Lapis itself is generally inert but may fluoresce weak of moderate green or yellowish green under short wavelength.|
|Color-Filter Reaction||Dull reddish brown.|
|Effects Caused by heat||Pale-colored stones sometimes darken and improve in appearance when brought to a dull-red heat, but an undesirable green may be produced. If heated too strongly, lapis will lose all color|
|Effects Caused by Acids||Decomposed slowly by hydrochloric acid, giving the odor of rotten eggs (hydrogen sulphide). The calcite matrix effervesces.|
|Effects Caused by irradiation||No effect|
The most widely used substitute for lapis for many years has been blue-dyed chalcedony. The main cause for confusion is not that it bears a close resemblance to lapis, but that the average jeweler is accustomed to seeing it and hearing it referred to by the trade names "German lapis" and "Swiss lapis". Actually, both the color and general appearance of dyed chalcedony differ markedly from lapis. Its fracture surfaces of lapis. However, the luster of its fractures is dull to waxy, not appreciably different than the luster of rough lapis. Usually, since chalcedony is well polished, an accurate R. I. reading can be taken; this permits a positive identification, because the reading is distinctly higher 0.53 compared to 1.50 than that of lapis. (Note: Because most specimens of lapis are poorly polished, it is difficult to determine R.I. when the polish is sufficiently good, it must be embarked that lapis is a rock and that the R.I. of the pyrite or calcite portions will be entirely different from that of the blue portion. Thus, care must be exercised to make certain that only the blue part is being tested ). A streak test is also valuable, since the streak of lapis is usually pale blue and chalcedony cuts into the testing plate, rather than leaving a streak.
Glass rarely has the same appearance as lapis; when it does however, it can be detected by swirl marks, mold marks, and especially gas bubbles, which are present in profusion and usually detectable under magnification near the surface. Moreover, the conchoidal, various fractures of glass are completely unlike the uneven, dull, granular fractures of lapis.
Opaque synthetic spinel is made that resembles good-quality lapis. Some of the stones made from this material even have metallic inclusions, which are produced by forcing pure gold into holes in the surface. These stones have a much higher luster than lapis and are usually well polished; thus, an R.I. determination will usually ascertain identify immediately. If doubt exists, the metal particles can be tested with a needle. The hard pyrite inclusions in the genuine material are difficult to scratch, but the gold particles in synthetic spinel are very soft by comparison and can be scratched with no effort.
There are three natural gem minerals that may resemble lapis very closely: azurite, lazulite and sodalite. If these stones are well polished and an R. I. can be obtained, both azurite and lazulite can be separated easily because of their much higher indices. However, the R.I. of sodalite is similar to that of lapis. If the index cannot be determined, or if sodalite is suspected, a separation can be effected by S.G. for both azurite and lazulite are noticeably higher than lapis and the value for sodalite is definitely lower. The difference in S.G. is particularly noticeable, since confusion would normally occur only with finer specimens of Lapis without pyrite inclusions. The presence of pyrite practically eliminates azurite and lazulite. Sodalite, a member of the same group of minerals as lapis, almost never contains pyrite, so this is of value in separation.
However, it is possible for sodalite to be one of the constituents in the rock that is lapis; as a practical matter, therefore, they are not far from being identical. S.G. does provide an effective means of separation, however, another less frequently encountered gem mineral that may bear a marked resemblance to lapis is the massive, violet-blue pyroxene known as violane. It can be distinguished by its higher R. I. (1.69) and S.G. (3.23)
Since lapis-lazuli is an opaque material in gem sizes, polariscope tests are obviously of no value. If acid tests are made, only a very small drop should be applied to the stack of a stone, in order to avoid damage. Afterward, it should be washed thoroughly.
For purposes of establishing the value of various grades of lapis lazuli, it is first necessary to distinguish between those qualities that are commercially available and those that can be described as exceptional and difficult to obtain. Exceptional qualities are logically subdivided into three classifications, as follows (all prices given are wholesale per stone values based on 13 x 18 millimeter cabochons):
Stones in this category are an intense, slightly dark violetish blue. They are evenly colored, entirely free of calcite or pyrite and have a superior polish. Prices range from $200 to $480 per stone. (Note: Larger stones may be sold by the carat for as much as $40 per carat.)
Cabochons of second quality have the same qualifications as those listed above, except that the color is either pure blue or violet-blue. Prices range from $120 to $400 per stone.
The color and other attributes of these stones are equal to those of the first or second type, but they are characterized by an attractive, even distribution of small pyrite crystals over the entire surface. Prices range from $40 to $160 per stone.
Stones that are normally available in commercial quantity contain varying amounts of pyrite and/or calcite; of these, calcite is the least desirable. In addition, the color is often low in intensity and unevenly distributed and the polish inferior. Prices range from as little as $1 to $40 per stone. The least expensive are those containing a high percentage of large white areas. Those containing little pyrite and almost no calcite are the most expensive in this group.
For may years a prominent man in the jewelry industry has worn a handsome ring set with lapis. It has been a source of constant pleasure for him, for he enjoys both its beauty of color and the conversations about it initiated by friends and strangers alike.
These are among the dividends that accrue to wearers of lovely stone-set jewelry. Although women are interested in most of the colored stones, and any person can wear most of them, there are fewer gemstones that are particularly suitable for most men. Lapis is an excellent stone for men jewelry, whether for great cufflinks, rings, tie clips or other items.
Although lapis was arbitrarily removed from the official birthstone list, it is properly considered a birthstone for December with better factual basis than for many of the other birthstones. However, this is seldom of any importance in selling lapis jewelry (but it may be significant if his wife is obtaining the jewelry for him as a gift).
There is little enough lapis offered for sate today that a good case may be made for choosing it for a man who is regarded as a leader in the community. That you consider him a leader and thus recommend an unusual and pace-setting piece of jewelry is flattering to him and/or his loved ones. Thus, those who enjoy the lovely intense blue color of lapis when it is pointed out to them may be led to recognize the other pleasures its ownership brings. Since even the best qualities are comparatively inexpensive, a good selection of lapis jewelry can enhance the attractiveness and eye appeal of any showcase.