Presentation is loading. Please wait.

Presentation is loading. Please wait.

References Dietmar Schwarz, 2542. เอกสารประกอบการ อบรมเชิงปฏิบัติการเรื่อง “ มรกต และพลอยตระกูลคอรันดัม “. ภาควิชา.

Similar presentations


Presentation on theme: "References Dietmar Schwarz, 2542. เอกสารประกอบการ อบรมเชิงปฏิบัติการเรื่อง “ มรกต และพลอยตระกูลคอรันดัม “. ภาควิชา."— Presentation transcript:

1 References Dietmar Schwarz, เอกสารประกอบการ อบรมเชิงปฏิบัติการเรื่อง “ มรกต และพลอยตระกูลคอรันดัม “. ภาควิชา ธรณีวิทยา มหาวิทยาลัยเชียงใหม่ Delaney,J.V.Patrick, Gemstones of Brazil-Geology and Occurrences.REM-revista Escola de Minas, Brazil Fischer,M., The emeralds of the Belmont-Mine, Minas Gerais, Brazil. J.Gemm. 20, Giuliani, G., and others, Origin of emerald deposits of Brazil. Mineralium Deposita 25, Emerald Deposits of Brazil

2 The search for emeralds in Brazil began about 500 years ago, after the arrival of the Portuguese in the country, however only in 1963 the first samples of the stone with real commercial value were found in the mine of Salininha, in Bahia, wiping out the old idea that Brazil had no precious stones.

3

4 History 16-17th centuries : in search of the legendar “Serra das Esmeraldas” beginning of 20th century : discovered some small deposits in Bahia state 1963 first important find of emeralds in Salininha mine, Bahia 1978 accidentally discovery of emerald deposit (Blemont Mine) in Minas Gerais 1981 emerald mining (Blemont Mine) started 1981 discovery of Santa Terezinha emerald deposits in Goias State 1983 emerald mining started in Socoto area, Bahia 1988 discovery of Capoeirana deposits near Belmont Mine 1997 discovery of emeralds in the Amazon region in the area called Monte Santo, Tocantins State

5 BAHIA MINAS GERAIS GOIA`S Emerald productio n in Brazil is concentra ted in these three states

6 Geology Basement of Archean Gneiss Complex (> 2.5 Ga.) Overlies by Proterozoic mafic-ultramafic and meta -sedimentary/volcanic rocks Classification of Emerald Deposits Granitic Pegmatite-Hydrothermal Type I/A In mafic-ultramafic rocks : Carnaiba- Socoto (2.0 Ga.), Belmont Mine- Capoeirana (508 Ma.) Tectonic-Hydrothermal Type II/A In volcano - sedimentary rocks : Santa Terezinha (520 Ma.)

7 Brazilian Emeralds Major producers: Salininha and Carnaiba Districts, Bahia; Santa Terezinha District, Goias; Nova Era and Itabira Districts, Minas Gerias. Occurrences: alluvial, hydrothermal and pegmatite deposits Chromophore is V in some stones, not Cr as in most other emeralds. Brazilian emeralds were once thought of as typically lighter-toned and much yellower compared to other sources. As for all generalities, there are many exceptions; Santa Terezinha has produced emeralds of exceptional color, though mostly of small size.

8 Mining & Production Supervised by Federal Mining Department ( DNPM) Mining claim (5years) = US$ 2 million Mining cost per 1 kg rough = US$ m advance of shaft and tunnel = US$ Annual production = US$ 50 million Santa Terezinha, Goia’s State = 60 % Carnaiba & Socoto, Bahia State = 30 % Itabira & Nova Era, Minas Gerais State = 10 %

9 Goia’s: The "garimpo" is located in the municipality of Campos Verdes. Nowadays few companies explore there as the known mines are very deep (up to 600 meters deep), thus not permitting their exploration by "garimpeiros"(garimpo workers). The gems are of very small sizes but with good crystallization. At present the production is small in volume and of lower commercial quality. Bahia: This "garimpo" presents a very irregular production owing to its geological characteristics, but it provides with a reasonable quantity of rough material adequate for cutting, reaching competitive prices in the market. The production varies from lower, commercial to extra goods in all sizes. At present this "garimpo" is producing a reasonable amount of rough and tending to increase production in the near future. Minas Gerais: The production is concentrated in two places, one of them is Itabira, the only emerald mining activity enterprise in Brazil explored by just one company, a partner of CANELHAS that consumes % of the total production. Its production is quite steady and homogeneous in clarity and colour..

10 Nova Era, is a region close to Itabira. It is a more recent "garimpo" and its goods began to be accepted in the international market at the beginning of They are clearer crystals of bigger sizes with a bright shine. At present its production is small and irregular, what has reduced the market for this kind of product. Nova Era Mine, Minas Gerais

11 MINING AT NOVO ERA AREA

12 The discovery of the mine of Salininha and the international acceptance of its gems changed the characteristics of the search for emeralds in Brazil, increasing the mining activity in the country, what brought about the discovery of new mines raising the country to one of the first positions in the world production of colored gems, besides being an important source of emeralds with very good quality. Salininha Mine, Bahia

13

14 Emerald Deposits of South Asia (Afghanistan, Pakistan and India) Afghanistan 1 : Panjshir Valley India 2 : Arawalli Mtn., Rajasthan Pakistan 3 : Swat Valley Khaltar Valley (Khaltaro) 2 1 3

15 AFGHANISTAN Tectonic hydrothermal of type II/A2 (Hydrothermal veins cutting ophiolites) Panjshir Valley 130 km N. of Kabul discovered early 1970s peak production of 1990s (US$ 10 mil. for rough) source of revenue for Mujahideen ! difficult terrain, lacks of infrastucture mining activities depend on political and military situations ! Ref. Emeralds of the Panjshir Valley, Afghanistan in GEMS & GEMOLOGY, Spring, 1991

16 Panjshir Valley, Afghanistan with the background of Hindugush Mtn.

17 Arial view of Panjshir Valley

18 Village of Khenj in Panjshir Valley. The village is like a boom town where emerald miners buy their supplies and food on the way to the emerald mines in the mountains.

19 Emerald miners at Khenj standing in front of a covered generator left by the Russian army. The miners were able to get this generator into operating condition for use in their mining operation.

20

21 Emerald miners showing off their new Swiss drill at an emerald mine located above the Village of Mekini, Panjshir Valley, Afghanistan.

22

23 Emerald miners standing in front of their tunnel in Panjshir Valley, Afghanistan. The openings of most shafts are three to four feet high and approximately three feet wide.

24 Green emerald crystals on the roof of an emerald tunnel.

25

26

27 A carats Panjshir emerld crystal

28 PAKISTAN Swat Valley : Type II/A2 (Hydrothermal veins cutting Mingora ophiolites melange) Mingora deposits Makhad deposits Guajar Kili deposits Khaltaro : Type I/A (Pegmatite culling mafic-ultramafic rocks) Khaltar Valley deposits near Khaltaro village Kazni,A.H. and Snee,L.W., Emeralds of Pakistan. Elite Publishers Ltd. Pakistan

29 MINGORA (Swat Valley) found in 1958 near Mingora City, Swat District fine emeralds comparable to Muzo’s known as “Pakistan or Swat Emeralds” Mining done by GEMCP (Gemstone Corp. of Pakistan). Mineralization in shear planes, fractures, stockworks and tension gashes cm emerald-bearing zone around quartz lenses Commonly up to 30 carats crystals of good green colour and clarity.

30 MAKHAD (Swat Valley) near Makhad Village, 19 Km NE of Mingora intermittenly mined (Local and GEMCP) Emerald crystals (10 carats or greater) in talc- carbonate schist host rocks very dark green, opaque to translucent, full of inclusions (talc, carbonate minerals etc.). low gemmological value. now abandoned

31 GUJAR KILI (Swat Valley) 24 Km ENE of Mingora discovered in 1981 by GEMCP 3 acres outcrop of Mingora ophiolite melange faulted and fractured talc-carbonate host rocks limonitization is the dominant wall-rock alteration emeralds in limonitzed fault and joint planes large crystals are carats weight deep blue green, transp.-transl., few inclusions since 1982 annual production > 10,000 carats

32 KHALTARO the deposit is at 4,500 m MSL, rugged terrain emeralds in peg. intruded mafic-ultramafic rks. 3 months mining periods (July-September) mostly 1-3 cm. euhedral crystals inclusions and cracks are common known production only 600 carats by GEMCP

33 INDIA Type I/A (Pegmatite culling mafic-ultramafic rocks) Inclusions reflect mineralogy of host rock e.g. talc, Cr-mica (fuchsite), biotite, apatite etc. Comma shaped fluid inclusion (similar to those from Santa Terrezinha, Brazil) Mined since 1955 at Arawalli Mountain, Rajasthan 200 km belt of Precambrian schists intersected by altered peridotite bodies, pegmatites and granites.

34 Emerald Deposits of Europe AUSTRIA Habachtal deposit mined during Roman Empire RUSSIA Takovaya-Malysheva deposits NORWAY Eidsvoll deposits NORWAY

35 Ekaterinburg Takovaya-Malysheva Eidsvoll Habachtal

36 RUSSIA deposits in Ural area, 90 Km NE of Ekaterinburg discovered by Maxim Kojevenikov near Takovaya river in 1830 (mine opened in 1831) during WW II was the main source for Be 3-4 mil. carats of emerald and green beryl per year in 1950s underground mining at Takovaya-Malysheva since 1970s non-profitable mining and marketting problems by ends of 1990s

37 Australia has been a fairly important producer of emeralds. Several important sites in New South Wales and Western Australia have been described. Many of the emeralds that have been shown in colored prints are probably closer to green beryl but some fine blue green stones are known. Emerald Deposits of Australia Poona deposits Emmaville-Torrington deposits

38 Emerald Deposits of Africa Colored gemstone mining in Africa is very different however. The vast majority of the colored gemstone production is produced by small scale miners often using only picks, chisels, hammers and shovels. Many of these small scale miners are "illegal" (unlicensed) and often mine until their food runs out or the mining becomes too difficult. NG EG SA MZ SM M TZ ZA ZB

39 Ndola Rural emerald deposit, 200 Km north of Lusaka (S.G.=2.75; R.I. E =1.583, R.I. O =1.590) Once a major producer;40% of all emeralds sold in U.S. in 1989 where from this source. In schists adjacent to pegmatites; can contain tourmaline and biotite inclusions. Lusaka Excellent clarity, but often darker, with a more noticeably bluish cast than Colombian emerald. ZAMBIA

40 Zambian emeralds, though not as prevalent in the market as those from Colombia or Brazil, are easy to love and worth seeking out for their deep tones, clarity and generally lower prices. A source in Zambia says the domestic emerald industry is healthy, with some big operators such as the Kamakanga Mine and Kagem. A majority of emeralds still exit the country illegally, though the Ministry of Mines reported production figures of 588 kg of emerald in 1996, up 350% from 1995.

41 Kamakanga Emerald Area, Ndola Rural, Zambia August 1984 In the emerald producing area of Zambia, much of the exploration and mining is done by tunneling underground. The miners and I are looking for a rock formation of mica-chlorite schist in contact with a pegmatite which is were emerald mineralization occurs. Although many miners are injured and even die working under these conditions, malaria in the bush areas was a much greater health risk and claims many lives.

42 Sandawana Valley Deposits S.G.=2.755; R.I. E =1.586, R.I. O =1.593 Mostly small stones (0.5 carat or smaller), heavily flawed in larger sizes Excellent colour In schists invaded by pegmatites and quartz veins Noted for inclusions of acicular tremolite, and for somewhat higher R.I. than Colombian and Brazilian emeralds. Zimbabwe Salisbury

43 Emerald Deposits of North America Hidden, North Carolina

44 In the United States, few emeralds have been found and most have been recovered from near Hidden, North Carolina. A very large emerald that became the subject of a bitter law suit was mined there in the 1980's. The tragicomic outcome was that one of the miners involved sawed the very fine 14 inch crystal (valued at several millions of dollars) in half and destroyed much of the value of this essentially priceless item. Except for the North Carolina finds, no other state has had any significant emerald production. p?NTYPEID=7&NNEWSID=966 USA

45 Over the next hundred years, the Hiddenite area saw "emerald rushes" come in go, with significant specimens unearthed in 1906, 1969, 1971 and In 1995, fresh off the discovery of a carat gem- quality emerald, Hill set up North American Emerald Mines to thoroughly comb the old Rist Mine, which produced over 3,500 carats of emerald rough during its heyday in the early '80s, as well as previously unexplored areas. James King Hill Jr. proudly shows off his latest emerald find in Hiddenite, North Carolina.

46 Aquamarine Deposits Africa : Madagascar, Namibia, Nigeria, Zambia, Zimbabwe America : Brazil, USA Europe : Russia, N. Ireland Asia : Afghanistan, India, Pakistan, Sri Lamka AQUAMARINE DEPOSITS

47 Aquamarine Birthstone for the month of March. Name is applied to blue to greenish- blue to bluish-green ("sea green") beryl. Most common untreated material is greenish-blue, although very light to medium blue varieties are by no means rare. Found exclusively in pegmatites, or as water worn, frosted pebbles or cobbles in stream gravels. known. Africa : Madagascar,Na mibia, Nigeria, Zambia, Zimbabwe America : Brazil, USA Europe : Russia, N. Ireland Asia : Afghanistan, India, Pakistan, Sri Lamka

48 Most important source, mostly from the state of Minas Gerais, near the town of Teofilo Otoni. Famous but now depleted deposit of Santa Maria noted for exceptional deep "electric" blue aqua.Minas Gerais Common lighter blue aqua shows deepest color only in stones of 5-10 cts. or more. Blue-green stones sometimes referred to "Brazilian Aqua." BRAZIL

49 Ground-piercing radar to prospect for gemstone deposits in Brazil Prospectors have utilized a whole range of methods to locate precious gems. Some of these methods are scientific, some pseudo-scientific, some employ common sense and others are just plain bizarre.

50

51 Africa Madagascar - usually medium dark blue. Darker aqua. sometimes referred to as "Madagascar Aqua." Africa (Namibia, Nigeria, Zambia, Zimbabwe) - mostly since Noted for untreated, deeper blue color that persists in even the smallest cut stones carat gems retain a "spectacular" deep blue. Most Nigerian stones show a slight green overtone that cannot be removed by heat treatment (Cr is chromophore, rather than Fe present in treated Brazilian aqua.).

52 Kapilinkesa Aquamarine Mine, Lukusuzi National Park, As the mine was located in a national park, no mechanized operations were allowed. All mining was done by hand and by utilizing large fires. As in the picture, these large fires were used to break the large quartz pegmatite. The fires were set in the late afternoon and were allowed to burn throughout the night. The heat would crack the rocks and allow for easier breaking by sledgehammers. The mining here is an example of how a typical small scale mine operates although the utilization of fire was very innovative. ZAMBIA

53 Mining in remote areas is very difficult. As we were 120 miles from the nearest town on very bad bush roads, being self sufficient in our operation was essential. In this picture, we are sharpening steel chisels after first softening them in a homemade kiln and then pounding them to a sharp point. This was a constant chore and one that all small scale miners used. Kapilinkesa Mine, Lukusuzi National Park, Zambia

54 The production of aquamarine raw crystals just after they are pulled from the ground. From this stage the crystals are broken up and chipped clean with tungsten pliers to expose the "clean" gemmy areas. This is a very tedious and long process as it must be done very carefully to preserve as much of the gem areas as possible. Only a small percentage of the crystals actually yielded clean gemmy pieces.

55 Kapilinkesa Mine, Lukusuzi National Park, Zambia A crystal fragment of top quality aquamarine only minutes after it was mined. After separating, it yielded a 5 gram absolute gem piece! It is moments like this that all gemstone miners wait for.

56 This is very fine material, after 2 months production, and it was all sold immediately to a well known Brazilian dealer who then called it of Brazilian origin after cutting and polishing. Most of the production, as in all gemstone mines is in the smaller sizes.

57 A 169 carat aquamarine from Nuristan, Afghanistan faceted by Allen Pobanz. Valued at $85,000. AFGHANISTAN A set of aquamarine crystals from Nuristan, Afghanistan

58 Beautiful 2 1/2 inch high Aquamarine crystals in mica from Nuristan, Afghanistan. Priced at $

59 Gems from Pech Nuristan Nuristanis with Gems

60 END OF BERYL SHOW

61 A STATUS REPORT ON GEMSTONES FROM AFGHANISTAN By Gary W. Bowersox © 1986 Gemological Institute of America First published in GEMS & GEMOLOGY, Winter, Suggested Reading


Download ppt "References Dietmar Schwarz, 2542. เอกสารประกอบการ อบรมเชิงปฏิบัติการเรื่อง “ มรกต และพลอยตระกูลคอรันดัม “. ภาควิชา."

Similar presentations


Ads by Google