( GIC Founder of Taiwan , Principal of World Gem Identification and Study Center , Chairman of GIC alumni association of Taiwan , Chairman of R.O.C.G.A. )
Abstract：Blue chalcedony is a special local gemstone in Taiwan. Taiwan blue chalcedony owes beauty and popularity to its vivid blue－green or blue color ,and its value is the highest among the jade that produced in Taiwan. It also outshines others in the world market. Blue chalcedony from Taiwan was found in the mountain-seacoast of eastern Taiwan , and its occurrence belongs to hydrothermal deposit. The blue chalcedony from Taiwan is compared with its simulants in details. Besides,the writer investigates the chalcedony diggings of Donghe village in Taidong county for distribution and causation.
Key words： Blue chalcedony, mountain-seacoast, Taiwan
Chart of distribution of Taiwan blue chalcedony in the mountain- seacoast
0.Preface
Local precious gemstones in Taiwan except amphibole are the blue chalcedony. This kind of extensive distribution in mountain-seacoast of eastern Taiwan was found in the time of colonial era of Japan . (was named "Taiwan blue gem " "Taiwan blue color gemstone "), which was mined since 1960s.Blue chalcedony remains the highest value in Taiwan due to decreasing output and increasing requirement.
1.Distribution
Taiwan blue chalcedony usually distributes among the mountain-seacoast of eastern Taiwan ,the north range from Fongbin village of Hualian county , and the south range to Dulan village of Taidong county,that blue chalcedony spread between this two areas.Producing area of blue chalcedony are in mountain-seacoast ,which are cliffy ,in the face of Pacific Ocean,and the altitude from 500m to 1600m.The occurrence of blue chalcedony belongs to hydrothermal deposit ,thatis often found as a late hydrothermal deposit or an alteration product in acidic or basic igneous rocks, tuffs and breccias.Component of copper and silicone dioxide formed beautiful blue chalcedony,which often with chrysocolla inside.
Taiwan blue chalcedony is often blue or blue-green color, and copper is the major color causation, component about 0.01%~0.02%.Part of blue chalcedony were changed color in “blue-white” due to over heating while processing.If the heat over 200℃,color was changed without return because of water release and copper oxidization.
Bangle of Taiwan blue chalcedony
2.Commerce situation
Exploitation of blue chalcedony since colonial era , and the high quality products were sold to Japan market in the 1960s.Until 10s years ago ,antecedents supplied simulants in Taiwan market from America (chrysocolla) ,or another blue chalcedony from Indonesia,that these were processed in Taiwan for market requirement,but the price were usually lower than Taiwan’s . Some products maybe simulate in color,but most of them have no better quality than Taiwan chalcedony,so price remains higher . Go on a tour of Hualian ,and Taidong city,you will find some shops exhibit Taiwan blue chalcedony (even if they are simulants from Indonesia , or New Mexico state of USA),the price are ranging between hundreds and thousands of N.T. dollars.Especially, unique one are waiting for a good price to sell,furthermore,the resident population of western Taiwan also know what is Taiwan blue chalcedony,so as to the value keeping high level all the time.
Chrysocolla
3.Analogous mimic
Because Taiwan blue chalcedony strongly receive favor on market, then huge amount of mimics launch on Taiwan markets, shoddy, or spurious mix the false with the genuine. Especially, Indonesia imports have the most quantity and near physical characteristic .Besides,simulants also have the kind of hemimorphite, dyeing blue chalcedony, turquoise and blue glass .Introduction as follows :
3.1Chrysocolla (see figure)
Chemical composition :(Ca, Al)2H2Si2O5(OH)2．nH2O,often contain copper and impurity.
Crystal habit : aphanitic or lump aggregate body, for copper mineral corrade alteration, often company with chalcedony .
Mohs’ scale of hardness :2~4, chalcedony accrete can heighten,
Relative density :2.0~2.4 g/cm3.
Refractive index :1.461~1.570.
Blare : wax to glass blare.
Color : green, blue-green, some can display water blue.
Distribution : Taiwan, America, Brazil, Chile, Peru.
Distribution : China, Austria, America, England, Germany.
.
Dyed ( blue ) chalcedony
3.3Dyed ( blue ) chalcedony (see figure)
Chemical composition :SiO2, but contain many kinds of dyes.
Crystal habit : aphanitic aggregate body, display lump, graininess or fine thin fibrous aggregates body.
Mohs’ scale of hardness: 6~7.
Relative density :2.60± 0.10 g/cm3.
Refractive index : about 1.54 (point measure ).
Blare : grease to glass blare.
Color : many kinds of colors.
Distribution : spread in the world because it is a mimic.
Blue glass --see flow line
3.4Blue glass (see figure)
Chemical composition :SiO2 and a little amount of metallic element.
Crystal condition : not a crystal quality body.
Mohs’ scale of hardness :5~5.5.
Relative density :2.30~2.60.
Refractive index : about 1.50.
Blare : wax to glass blare.
Turquoise
3.5 Turquoise (see figure)
Chemical composition : CuAl6[PO4]4(OH)8．4H2O.
Crystal system :triclinic system.
Crystal habit : aphanitic aggregate body ,display lump, tubercle , or nervation .
Mohs’ scale of hardness:5.5~6.
Relative density :2.4~2.9.
Refractive index : about 1.62
Blare : wax ~ earthy blare.
Distribution : Turkey, China, Iran, Egypt, America, Australia.
Ore of Taiwan blue chalcedony
4.Conclusion
Though several countries produce blue chalcedony and chrysocolla mineral in the world,for example Indonesia, America, and Chile, experts still think that Taiwan blue chalcedony is the most beautiful one.Because it outshines a kind of fresh gorgeous blue or slightly emerald green (see figure). Its quality is between opacity to transparency, which outshines after polishing. Now we show the comparison of Taiwan blue chalcedony and its simulants as follows: (see table).
Comparison of Taiwan blue chalcedony and its simulants
Kind
relative density
Mohs’ scale of hardness
transparency
color
refractive index
magnification
other
Taiwan blue chalcedony
2.58
6～6.5
slight transparency to translucency
blue, blue-green, more deep and pure color than other simulants
about 1.539
some contain ferrum jasper
no reaction in acid solution
Chrysocolla
2.0～2.4
2～4
not clear to translucency
green，blue-green
1.461～1.570
green strip or band
corrade in acid solution
Hemimorphite
3.45
4.5～5
not clear to slight transparency
green,
water blue
1.614～1.636
no characteristic
dissolve in
hydrochloric acid,but no air bubble
Dyed (blue)chalcedony
2.60
6～7
slight transparency to translucency
blue-green
about 1.540
dyes display granulose assemble
no reaction in acid solution
Blue glass
2.30～2.60
5～5.5
slight transparency to translucency
water blue
ablut 1.50
flow line and air bubble
no reaction in acid solution
Turquoise
2.76
5～6
not clear
blue to blue-green
about 1.61
ferric line and dark color matrix
dissolve in hydrochloric solution
The writer pointed out where the Taiwan blue chalcedony ore is
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