Diamonds are found in three types of deposits.
- alluvial
- glacial tills
- kimberlite / lamproite pipes
Sunday, February 18, 2007
A Beautiful Mind Movie
Memorable quote (s) from the movie:
Alicia (Jennifer Connelly): How big is the universe?
Nash (Russell Crowe): Infinite.
Alicia (Jennifer Connelly): How do you know?
Nash (Russell Crowe): I know because all the data indicates it's infinite.
Alicia (Jennifer Connelly): But it hasn't been proven yet.
Nash (Russell Crowe): No.
Alicia (Jennifer Connelly): You haven't seen it.
Nash (Russell Crowe): No.
Alicia Jennifer Connelly): How do you know for sure?
Nash (Russell Crowe): I don't, I just believe it.
Alicia (Jennifer Connelly): It's the same with love I guess.
Alicia (Jennifer Connelly): How big is the universe?
Nash (Russell Crowe): Infinite.
Alicia (Jennifer Connelly): How do you know?
Nash (Russell Crowe): I know because all the data indicates it's infinite.
Alicia (Jennifer Connelly): But it hasn't been proven yet.
Nash (Russell Crowe): No.
Alicia (Jennifer Connelly): You haven't seen it.
Nash (Russell Crowe): No.
Alicia Jennifer Connelly): How do you know for sure?
Nash (Russell Crowe): I don't, I just believe it.
Alicia (Jennifer Connelly): It's the same with love I guess.
Doing Business In Africa
World Bank / IFC writes:
Last year and the year before, Africa lagged behind all other regions in the pace of reform. This year it ranks third, behind only Eastern Europe and Central Asia and the OECD high-income countries (figure 1.2). Two-thirds of African countries made at least one reform, and Tanzania and Ghana rank among the top 10 reformers.
Some examples of what African countries reformed include:
In Côte d’Ivoire registering property took 397 days in 2005. Reforms eliminated a requirement to obtain the urban minister’s consent to transfer property. Now it takes 32 days.
Burkina Faso cut the procedures for starting a business from 12 to 8 and the time from 45 days to 34.
Madagascar reduced the minimum capital for start-ups from 10 million francs to 2 million.
Tanzania introduced electronic data interchange and risk-based inspections at customs. The time to clear imports fell by 12 days.
Gambia, Nigeria, and Tanzania reduced delays in the courts. More improvements are under way, and these will be reflected in the Doing Business indicators next year.
Benin, Burkina Faso, Cameroon, Gambia, Madagascar, Malawi, Mali, Mozambique, Niger, Nigeria, and Zambia have all started to simplify business regulation. The easy reforms—what can be done by the stroke of a minister’s pen—are coming first. Small as these initial reforms may be, they can attract investors who seek the growth opportunities that will follow. India’s economic boom may have started with just such reforms in the 1980s.
Several African countries are more ambitious. Mauritius set a goal of reaching the top 10 on the ease of doing business by 2009. It has targeted numerous areas of reform: making labor regulation more flexible, reducing the burden of paying taxes and speeding business entry and property registration. One reform: starting in 2007 every business will receive a unique business registration number, and entrepreneurs will no longer have to register in person for the income tax, value added tax, customs and social security numbers. The aim is to have data move around inside the government, not to have entrepreneurs run around from one office to another.
More info @ http://www.doingbusiness.org/main/Africa_Reforms.aspx
Last year and the year before, Africa lagged behind all other regions in the pace of reform. This year it ranks third, behind only Eastern Europe and Central Asia and the OECD high-income countries (figure 1.2). Two-thirds of African countries made at least one reform, and Tanzania and Ghana rank among the top 10 reformers.
Some examples of what African countries reformed include:
In Côte d’Ivoire registering property took 397 days in 2005. Reforms eliminated a requirement to obtain the urban minister’s consent to transfer property. Now it takes 32 days.
Burkina Faso cut the procedures for starting a business from 12 to 8 and the time from 45 days to 34.
Madagascar reduced the minimum capital for start-ups from 10 million francs to 2 million.
Tanzania introduced electronic data interchange and risk-based inspections at customs. The time to clear imports fell by 12 days.
Gambia, Nigeria, and Tanzania reduced delays in the courts. More improvements are under way, and these will be reflected in the Doing Business indicators next year.
Benin, Burkina Faso, Cameroon, Gambia, Madagascar, Malawi, Mali, Mozambique, Niger, Nigeria, and Zambia have all started to simplify business regulation. The easy reforms—what can be done by the stroke of a minister’s pen—are coming first. Small as these initial reforms may be, they can attract investors who seek the growth opportunities that will follow. India’s economic boom may have started with just such reforms in the 1980s.
Several African countries are more ambitious. Mauritius set a goal of reaching the top 10 on the ease of doing business by 2009. It has targeted numerous areas of reform: making labor regulation more flexible, reducing the burden of paying taxes and speeding business entry and property registration. One reform: starting in 2007 every business will receive a unique business registration number, and entrepreneurs will no longer have to register in person for the income tax, value added tax, customs and social security numbers. The aim is to have data move around inside the government, not to have entrepreneurs run around from one office to another.
More info @ http://www.doingbusiness.org/main/Africa_Reforms.aspx
The Federal Trade Commission’s Guide for the Jewelry, Precious Metals and Pewter Industries
FTC writes:
23.24 Misuse of the words "real," "genuine," "natural," "precious," etc.
It is unfair or deceptive to use the word "real," "genuine," "natural," "precious," "semi-precious," or similar terms to describe any industry product that is manufactured or produced artificially.
More info @ http://www.ftc.gov/bcp/guides/jewel-gd.htm
23.24 Misuse of the words "real," "genuine," "natural," "precious," etc.
It is unfair or deceptive to use the word "real," "genuine," "natural," "precious," "semi-precious," or similar terms to describe any industry product that is manufactured or produced artificially.
More info @ http://www.ftc.gov/bcp/guides/jewel-gd.htm
Precious Stones And Gems
By Edwin W Streeter
George Bell & Sons
1884
Edwin W Streeter writes:
Many pages have been written on the history of precious stones. Authorities on authorities, from remote antiquity to this our day, have been cited as to their value, their uses, their beauties, and their properties, but still one might venture to say that there are fewer judges of the genuineness and real value of precious stones than there are treatises to guide people to such knowledge. Would it be altogether unwarrantable to express a grave doubt whether even in the trade there are very many skilled in detecting the real measure of difference between one stone and another, either by that most essential test, the specific gravity, or by minor tests of a more trivial character? Be this as it may, I have arrived at the deliberate conviction, as a merchant and dealer long versed in the purchase and sale of gems, that some practical and popular guide to those who have an interest in ascertaining and testing the genuineness and value of precious stones, is urgently needed, and cannot fail to be generally useful.
As an illustration of the difficulties of the subject, it may be stated that Professor Church, in a lecture delivered the Society of Arts on April 6th, 1881, pointed out a number of errors in the identification of a collection of precious stones which had been exhibited for years at the South Kensington Museum, although the official description of these stones had been confided to a well-known professor of mineralogy and expert in gems.
In the division of family jewels much injustice is often done by persons incompetent to form a correct opinion of their relative values. A study of this handbook may serve to demonstrate the difficulty of an accurate discrimination. In all cases it would be wise to submit the jewels to a practiced judge, whether for valuation or for probate. It is not right to leave the decision to some house agent or mutual friend.
A lady had bequeathed to her some family jewels, consisting of a sapphire and diamond suite. As they had passed probate several times, there was no doubt in the mind of the legatee of the genuineness of the sapphires. On being applied to in relation to their value, I had to pronounce the sapphires to be only paste. Had they been genuine they would have realized from 30000 pounds to 40000 pounds.
One often sees the spinel and the balas—the one a lively poppy red, and the other a violet rose—usurping the dignity of the true ruby; and yet the pure ruby of ten carats is worth from 3800 pounds to 4800 pounds, while the other stones, called by the same name, would be dear at one hundred pounds.
A gem should be a real possession, capable of affording pleasure to the wearer and the spectator, and, with fair usage, retaining an intrinsic and marketable value, undiminished by the lapse of time. I have sometimes seen in wear gems so scratched that their luster has been seriously impaired, and a suspicion was thus excited in the minds of wearers, friends, and dealers, that there was a defect in the hardness of the stones, and consequently in their in genuineness. It may be worth while to point out that a small sum expended in repolishing such stones would restore their original luster, revive the pleasure derived from the possession of them, and prevent the risk of their being sold as paste or imitation jewelry.
The value of precious stones must vary to some extent with the caprice of fashion—a gem which at one period stands high in public favor being at another time less eagerly sought after. Thus the chrysolite of the ancients, though highly esteemed by them, has not retained its popular character.
It is quite pardonable, and of small consequence, that the characteristic of the less valuable gemstones should be comparatively unknown; but there are precious stones about which there should be no doubt in the mind either of the purchaser or the merchant, viz., the diamond, ruby, emerald, sapphire, opal, cat’s eye, alexandrite, and pearl.
In other matters the distinction between a genuine and fictitious material is generally well understood, and fastidiously recognized. A lady refuses to wear a gown composed of an inferior fabric, intended to represent silk, because of its color, texture, and draping indicate, to every experienced eye, the substitution of the false for the real; but she often seems to ignore the fact that the color, the brilliancy, and the texture of a true gem, are as distinguishable from those of the false or mere imitation, as the cotton is from the silk. We presume to believe that in the case of the gown, which in a few nights wear altogether loses its worth, the genuineness of the material is of far less consequence than it is in the case of gems, which should be heirlooms of value, not much deteriorated by the lapse of years.
In determining the value of gems, it should be borne in mind that a perfect stone is rarely met with; and that probably, not even ten percent of the stones which are brought into commerce are really of fine quality. In the mineral kingdom, as in other department of nature, perfection is almost unknown.
Much study and attention will be required to attain a knowledge of the properties and appearance of gems, but the subject is by no means unattractive, and may be turned to good account.
With objects such as those referred to above, I am publishing the present volume, the outcome of more than thirty seven years’ experience , and of the united knowledge of many men of science, and of my contemporaries in trade. I hope that it may be of some service to us as merchants, and to the public in general.
It must be borne in mind that this book is not intended to be a strictly scientific treatise, but rather a practical work for those who, whether in the trade or among the public at large, desire to obtain some knowledge of the general characteristics of precious stones and gems.
In conclusion, I trust that the Goldsmiths’ Company, as fathers of the trade, will ere long throw open their fine suite of rooms in Foster Lane, and will not only establish a comprehensive library of books bearing on the study of jewelry, but by giving gratuitous lectures on precious stones and precious metals will offer that aid to the younger members of our trade which is necessary for a proper understanding of their daily business. To this company we must also look for aids to the more general appreciation of fine art jewelry, by affording favorable opportunities for exhibitions, and by awarding prizes, similar to those offered by the Turner’ Company. This would give an impetus to study to those engaged in jewelry work, and would enable the public to obtain a more accurate knowledge of and to take a deeper interest in a subject which has hitherto remained the property of the exclusive few.
The legacies bequeathed to the Goldsmiths’ Company by the famous goldsmiths and jewelers of the 15th,16th, and 17th centuries, which have since increased in value to an extent almost inconceivable, without doubt were intended for some such purposes as those to which I have referred. I find that so early as 1415, a celebrated goldsmith, Sir Drugo Barentine, who was Lord Mayor of London in 1398, and again in 1408, gave faire lands to this Company.
For the subject matter which forms the basis of this volume, I am in an especial manner indebted to the work of Professor Kluge, translated by Mrs Brewer; and I have also to acknowledge my obligations to Major F B Beaumont, Mr James A Forster, and others who have obligingly contributed information.
George Bell & Sons
1884
Edwin W Streeter writes:
Many pages have been written on the history of precious stones. Authorities on authorities, from remote antiquity to this our day, have been cited as to their value, their uses, their beauties, and their properties, but still one might venture to say that there are fewer judges of the genuineness and real value of precious stones than there are treatises to guide people to such knowledge. Would it be altogether unwarrantable to express a grave doubt whether even in the trade there are very many skilled in detecting the real measure of difference between one stone and another, either by that most essential test, the specific gravity, or by minor tests of a more trivial character? Be this as it may, I have arrived at the deliberate conviction, as a merchant and dealer long versed in the purchase and sale of gems, that some practical and popular guide to those who have an interest in ascertaining and testing the genuineness and value of precious stones, is urgently needed, and cannot fail to be generally useful.
As an illustration of the difficulties of the subject, it may be stated that Professor Church, in a lecture delivered the Society of Arts on April 6th, 1881, pointed out a number of errors in the identification of a collection of precious stones which had been exhibited for years at the South Kensington Museum, although the official description of these stones had been confided to a well-known professor of mineralogy and expert in gems.
In the division of family jewels much injustice is often done by persons incompetent to form a correct opinion of their relative values. A study of this handbook may serve to demonstrate the difficulty of an accurate discrimination. In all cases it would be wise to submit the jewels to a practiced judge, whether for valuation or for probate. It is not right to leave the decision to some house agent or mutual friend.
A lady had bequeathed to her some family jewels, consisting of a sapphire and diamond suite. As they had passed probate several times, there was no doubt in the mind of the legatee of the genuineness of the sapphires. On being applied to in relation to their value, I had to pronounce the sapphires to be only paste. Had they been genuine they would have realized from 30000 pounds to 40000 pounds.
One often sees the spinel and the balas—the one a lively poppy red, and the other a violet rose—usurping the dignity of the true ruby; and yet the pure ruby of ten carats is worth from 3800 pounds to 4800 pounds, while the other stones, called by the same name, would be dear at one hundred pounds.
A gem should be a real possession, capable of affording pleasure to the wearer and the spectator, and, with fair usage, retaining an intrinsic and marketable value, undiminished by the lapse of time. I have sometimes seen in wear gems so scratched that their luster has been seriously impaired, and a suspicion was thus excited in the minds of wearers, friends, and dealers, that there was a defect in the hardness of the stones, and consequently in their in genuineness. It may be worth while to point out that a small sum expended in repolishing such stones would restore their original luster, revive the pleasure derived from the possession of them, and prevent the risk of their being sold as paste or imitation jewelry.
The value of precious stones must vary to some extent with the caprice of fashion—a gem which at one period stands high in public favor being at another time less eagerly sought after. Thus the chrysolite of the ancients, though highly esteemed by them, has not retained its popular character.
It is quite pardonable, and of small consequence, that the characteristic of the less valuable gemstones should be comparatively unknown; but there are precious stones about which there should be no doubt in the mind either of the purchaser or the merchant, viz., the diamond, ruby, emerald, sapphire, opal, cat’s eye, alexandrite, and pearl.
In other matters the distinction between a genuine and fictitious material is generally well understood, and fastidiously recognized. A lady refuses to wear a gown composed of an inferior fabric, intended to represent silk, because of its color, texture, and draping indicate, to every experienced eye, the substitution of the false for the real; but she often seems to ignore the fact that the color, the brilliancy, and the texture of a true gem, are as distinguishable from those of the false or mere imitation, as the cotton is from the silk. We presume to believe that in the case of the gown, which in a few nights wear altogether loses its worth, the genuineness of the material is of far less consequence than it is in the case of gems, which should be heirlooms of value, not much deteriorated by the lapse of years.
In determining the value of gems, it should be borne in mind that a perfect stone is rarely met with; and that probably, not even ten percent of the stones which are brought into commerce are really of fine quality. In the mineral kingdom, as in other department of nature, perfection is almost unknown.
Much study and attention will be required to attain a knowledge of the properties and appearance of gems, but the subject is by no means unattractive, and may be turned to good account.
With objects such as those referred to above, I am publishing the present volume, the outcome of more than thirty seven years’ experience , and of the united knowledge of many men of science, and of my contemporaries in trade. I hope that it may be of some service to us as merchants, and to the public in general.
It must be borne in mind that this book is not intended to be a strictly scientific treatise, but rather a practical work for those who, whether in the trade or among the public at large, desire to obtain some knowledge of the general characteristics of precious stones and gems.
In conclusion, I trust that the Goldsmiths’ Company, as fathers of the trade, will ere long throw open their fine suite of rooms in Foster Lane, and will not only establish a comprehensive library of books bearing on the study of jewelry, but by giving gratuitous lectures on precious stones and precious metals will offer that aid to the younger members of our trade which is necessary for a proper understanding of their daily business. To this company we must also look for aids to the more general appreciation of fine art jewelry, by affording favorable opportunities for exhibitions, and by awarding prizes, similar to those offered by the Turner’ Company. This would give an impetus to study to those engaged in jewelry work, and would enable the public to obtain a more accurate knowledge of and to take a deeper interest in a subject which has hitherto remained the property of the exclusive few.
The legacies bequeathed to the Goldsmiths’ Company by the famous goldsmiths and jewelers of the 15th,16th, and 17th centuries, which have since increased in value to an extent almost inconceivable, without doubt were intended for some such purposes as those to which I have referred. I find that so early as 1415, a celebrated goldsmith, Sir Drugo Barentine, who was Lord Mayor of London in 1398, and again in 1408, gave faire lands to this Company.
For the subject matter which forms the basis of this volume, I am in an especial manner indebted to the work of Professor Kluge, translated by Mrs Brewer; and I have also to acknowledge my obligations to Major F B Beaumont, Mr James A Forster, and others who have obligingly contributed information.
The Federal Trade Commission’s Guide for the Jewelry, Precious Metals and Pewter Industries
FTC writes:
23.23 Misuse of the words "ruby," "sapphire," "emerald," "topaz," "stone," "birthstone,"
"gemstone," etc.
(a) It is unfair or deceptive to use the unqualified words ruby, sapphire, emerald, topaz, or the name of any other precious or semi-precious stone to describe any product that is not in fact a natural stone of the type described.
(b) It is unfair or deceptive to use the word ruby, sapphire, emerald, topaz, or the name of any otherprecious or semi-precious stone, or the word stone, birthstone, gemstone,' or similar term to describe a laboratory grown, laboratory-created, [manufacturer name]-created, synthetic, imitation, or simulated stone, unless such word or name is immediately preceded with equal conspicuousness by the word laboratory-grown, laboratory-created, [manufacturer name]-created, synthetic, or by the word imitation or simulated, so as to disclose clearly the nature of the product and the fact it is not a natural gemstone.
Note to paragraph (b): The use of the word "faux" to describe a laboratory-created or imitation stone is not an adequate disclosure that the stone is not natural.
(c) It is unfair or deceptive to use the word "laboratory-grown," "laboratory-created," "[manufacturer name]-created," or "synthetic" with the name of any natural stone to describe any industry product unless such industry product has essentially the same optical, physical, and chemical properties as the stone named.
More info @ http://www.ftc.gov/bcp/guides/jewel-gd.htm
23.23 Misuse of the words "ruby," "sapphire," "emerald," "topaz," "stone," "birthstone,"
"gemstone," etc.
(a) It is unfair or deceptive to use the unqualified words ruby, sapphire, emerald, topaz, or the name of any other precious or semi-precious stone to describe any product that is not in fact a natural stone of the type described.
(b) It is unfair or deceptive to use the word ruby, sapphire, emerald, topaz, or the name of any otherprecious or semi-precious stone, or the word stone, birthstone, gemstone,' or similar term to describe a laboratory grown, laboratory-created, [manufacturer name]-created, synthetic, imitation, or simulated stone, unless such word or name is immediately preceded with equal conspicuousness by the word laboratory-grown, laboratory-created, [manufacturer name]-created, synthetic, or by the word imitation or simulated, so as to disclose clearly the nature of the product and the fact it is not a natural gemstone.
Note to paragraph (b): The use of the word "faux" to describe a laboratory-created or imitation stone is not an adequate disclosure that the stone is not natural.
(c) It is unfair or deceptive to use the word "laboratory-grown," "laboratory-created," "[manufacturer name]-created," or "synthetic" with the name of any natural stone to describe any industry product unless such industry product has essentially the same optical, physical, and chemical properties as the stone named.
More info @ http://www.ftc.gov/bcp/guides/jewel-gd.htm
Doing Business In Eastern Europe
World Bank/IFC writes:
Doing business became easier in Eastern European countries in 2005-2006, according to a new report by the World Bank and the International Finance Corporation (IFC). Thirty-eight reforms in 16 economies in the region reduced the time, cost, and hassle for businesses to comply with legal and administrative requirements.
Spurred by recent or prospective accession to the European Union, Eastern Europe reformed more than any other region, including Western Europe and other OECD countries.Romania is top reformer in the regionDoing Business 2007: How to Reform finds that Romania was the second most active reformer on the ease of doing business across 175 economies, implementing reforms to simplify business licensing and trading, easing access to credit, increasing labor market flexibility, and strengthening investor protection. Croatia was ranked seventh. The top 10 reformers are, in order, Georgia, Romania, Mexico, China, Peru, France, Croatia, Guatemala, Ghana, and Tanzania.
Doing Business 2007 also ranks 175 economies on the ease of doing business-covering 20 more economies than last year's report. The top-ranked countries in Eastern Europe are Lithuania (16), Estonia (17), and Latvia (24), followed by Slovakia (36) and Romania (47).
The 30 economies that score the highest on the ease of doing business are, in order, Singapore, New Zealand, the United States, Canada, Hong Kong (China), the United Kingdom, Denmark, Australia, Norway, Ireland, Japan, Iceland, Sweden, Finland, Switzerland, Lithuania, Estonia, Thailand, Puerto Rico, Belgium, Germany, the Netherlands, Korea, Latvia, Malaysia, Israel, St. Lucia, Chile, South Africa, and Austria.
The rankings track indicators of the time and cost to meet government requirements in business start-up, operation, trade, taxation, and closure. They do not track variables such as market size, macroeconomic policy, quality of infrastructure, currency volatility, investor perceptions, or crime rates.
Romania -- the top reformer in the region and second-ranked globally -- simplified procedures for obtaining building permits and set up a single office for processing applications. This reduced the time for obtaining construction licenses by 49 days. Reforms to labor laws allowed term contracts to extend to six years, encouraging businesses to hire first-time workers. New customs procedures cut the time to satisfy regulatory requirements for trading in half, to 14 days. Romania also broadened the scope of information available for potential borrowers and sped bankruptcy proceedings.
More info @ http://web.worldbank.org
Doing business became easier in Eastern European countries in 2005-2006, according to a new report by the World Bank and the International Finance Corporation (IFC). Thirty-eight reforms in 16 economies in the region reduced the time, cost, and hassle for businesses to comply with legal and administrative requirements.
Spurred by recent or prospective accession to the European Union, Eastern Europe reformed more than any other region, including Western Europe and other OECD countries.Romania is top reformer in the regionDoing Business 2007: How to Reform finds that Romania was the second most active reformer on the ease of doing business across 175 economies, implementing reforms to simplify business licensing and trading, easing access to credit, increasing labor market flexibility, and strengthening investor protection. Croatia was ranked seventh. The top 10 reformers are, in order, Georgia, Romania, Mexico, China, Peru, France, Croatia, Guatemala, Ghana, and Tanzania.
Doing Business 2007 also ranks 175 economies on the ease of doing business-covering 20 more economies than last year's report. The top-ranked countries in Eastern Europe are Lithuania (16), Estonia (17), and Latvia (24), followed by Slovakia (36) and Romania (47).
The 30 economies that score the highest on the ease of doing business are, in order, Singapore, New Zealand, the United States, Canada, Hong Kong (China), the United Kingdom, Denmark, Australia, Norway, Ireland, Japan, Iceland, Sweden, Finland, Switzerland, Lithuania, Estonia, Thailand, Puerto Rico, Belgium, Germany, the Netherlands, Korea, Latvia, Malaysia, Israel, St. Lucia, Chile, South Africa, and Austria.
The rankings track indicators of the time and cost to meet government requirements in business start-up, operation, trade, taxation, and closure. They do not track variables such as market size, macroeconomic policy, quality of infrastructure, currency volatility, investor perceptions, or crime rates.
Romania -- the top reformer in the region and second-ranked globally -- simplified procedures for obtaining building permits and set up a single office for processing applications. This reduced the time for obtaining construction licenses by 49 days. Reforms to labor laws allowed term contracts to extend to six years, encouraging businesses to hire first-time workers. New customs procedures cut the time to satisfy regulatory requirements for trading in half, to 14 days. Romania also broadened the scope of information available for potential borrowers and sped bankruptcy proceedings.
More info @ http://web.worldbank.org
Intarsia
What Is Intarsia?
(via Gem Cutting: A Lapidary’s Manual) John Sinkankas writes:
The ancient art of imbedding small bits of colored material in cement to cover and decorate walls, floors, and other surfaces is called mosaic. Mosaic work using gemstones is popular among amateur gem cutters since it is both decorative and utilitarian. Surplus gem material can be used to advantage in ordinary mosaics, while exceptionally fine mosaic projects can absorb better material that is too small or not quite good enough for cabochons or faceted gems.
A variation of classic mosaic work is called intarsia, or sometimes pietre dure, or Florentine mosaic work. In this style of mosaic, flat pieces of stone are fitted together as closely as possible to make designs and pictures, much as pieces of glass are joined to make stained glass windows. However, intarsia is never transparent; pieces are always cemented to a base of stone, wood or other hard material. Some kinds of intarsia are inlaid into stone panels, which are then flattened to a common level and polished.
The beauty and effectiveness of intarsia depend on the skill used in making designs and selecting various kinds of stone to cover areas of different color and textures. The Italian method of inlaying intarsia is to carve out flat-bottomed recesses in soft slate to receive thin slabs of gem material (cut based on a paper pattern). The edges of the recesses are carefully trimmed to make them square and to avoid unsightly chipping. Since black slate is used, it is not necessary to try for a very exact fit because any slight gaps will be filled with an asphaltic mastic cement that matches the slate color. A truly perfect polish is not practical with this method because the heat generated will make the mastic flow and allow sections of stone to shift. However, a well-moistened pitch lap should overcome these difficulties and allow application of an excellent natural polish.
(via Gem Cutting: A Lapidary’s Manual) John Sinkankas writes:
The ancient art of imbedding small bits of colored material in cement to cover and decorate walls, floors, and other surfaces is called mosaic. Mosaic work using gemstones is popular among amateur gem cutters since it is both decorative and utilitarian. Surplus gem material can be used to advantage in ordinary mosaics, while exceptionally fine mosaic projects can absorb better material that is too small or not quite good enough for cabochons or faceted gems.
A variation of classic mosaic work is called intarsia, or sometimes pietre dure, or Florentine mosaic work. In this style of mosaic, flat pieces of stone are fitted together as closely as possible to make designs and pictures, much as pieces of glass are joined to make stained glass windows. However, intarsia is never transparent; pieces are always cemented to a base of stone, wood or other hard material. Some kinds of intarsia are inlaid into stone panels, which are then flattened to a common level and polished.
The beauty and effectiveness of intarsia depend on the skill used in making designs and selecting various kinds of stone to cover areas of different color and textures. The Italian method of inlaying intarsia is to carve out flat-bottomed recesses in soft slate to receive thin slabs of gem material (cut based on a paper pattern). The edges of the recesses are carefully trimmed to make them square and to avoid unsightly chipping. Since black slate is used, it is not necessary to try for a very exact fit because any slight gaps will be filled with an asphaltic mastic cement that matches the slate color. A truly perfect polish is not practical with this method because the heat generated will make the mastic flow and allow sections of stone to shift. However, a well-moistened pitch lap should overcome these difficulties and allow application of an excellent natural polish.
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