Chalcedony

Big Photo

Chrysoprase
India
6.86 carats
© gemselect.com

Although in general terms Chalcedony is a fibrous cryptocrystalline variety of Quartz, recent studies have shown that much Chalcedony is a mixture of cryptocrystalline quartz and mogánite, another silica mineral related to quartz but with a different crystal structure.

Chalcedony is probably named after an ancient town at the Bosporus.

Yellow, orange and red-orange variety of chalcedony from Botswana is known as Citrus Chalcedony.

Chalcedony Gemstones by Colour

This table shows the variety of hues this gemstone can be found in. Click on a photo for more information.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Chalcedony Gemstones by Size

This table shows distribution of Chalcedony gemstone sizes that are listed on this site. This can give a good indication as to the general availability of this gemstone in different sizes.
Contributed photos
Lightest:0.17 cts
Heaviest:931.99 cts
Average:26.38 cts
Total photos:324
Do you have a larger Chalcedony? Why not upload a photo?
0.17ct to 93.35ct93.35ct to 186.53ct186.53ct to 279.72ct279.72ct to 372.90ct372.90ct to 466.08ct466.08ct to 559.26ct559.26ct to 652.44ct652.44ct to 745.63ct745.63ct to 838.81ct838.81ct to 931.99ct
General Information
A variety or type of:Quartz
Varieties/Types:
Agate - A banded variety of Chalcedony.
Iris Agate - An iridescent variety of Agate.
Onyx - A monochromatic Agate with black and white banding.
Sardonyx - A monochromatic Agate with red/brown and either black or white banding.
Binghamite - Chatoyant Chalcedony with fibres of hematite/goethite.
Bloodstone - A dark green/greenish-blue Chalcedony with small red blood-like spots.
Carnelian - A red to orange variety of Chalcedony.
Chrome-Chalcedony - Emerald green Chalcedony, colored by chromium.
Chrysoprase - A green Chalcedony coloured by inclusions of Ni minerals.
Dendritic Agate - A chalcedony containing contrasting branching, or dendritic, mineral inclusions.
Moss Agate - A translucent chalcedony containing green strands of chlorite.
Fire Agate - A variety of Agate containing iridescent spheroids of limonite.
Jasper - Jasper is a dense, opaque, microcrystalline variety of Chalcedony.
Dallasite - A variety of Jasper from Vancouver Island, British Columbia, Canada.
Orbicular Jasper - Jasper containing numerous spherical inclusions.
Petrified Wood - A decorative type of fossil wood where the original organic material has been replaced - usually by chalcedony, agate, opal, etc.
Pietersite - Chalcedony with embedded fibers of amphibole minerals, causing chatoyancy.
Sard - A brown to brownish-red translucent variety of Chalcedony.
Chemical Formula
SiO
 
2
Arthur Thomas, Gemstones (2009)
Photos of natural/un-cut material from mindat.org
Chalcedony Treatments
Routinely dyed, tests limited: look for dye concentration between grain boundaries, in fractures. Transmitted light: may show mosaic-like marking - Blue Chart Gem Identification, Herve Nicolas Lazzarelli, 2010, p 7
Physical Properties of Chalcedony
Mohs Hardness6.5 to 7
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
Specific Gravity2.55 to 2.70
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
Cleavage QualityNone
Walter Schumann, Gemstones of the world (2001)
FractureUneven
Walter Schumann, Gemstones of the world (2001) Shell-likeMore from other references
Optical Properties of Chalcedony
Refractive Index1.530 to 1.543
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
Optical CharacterUniaxial/+
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Birefringence0.003 to 0.009
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
PleochroismAbsent
Walter Schumann, Gemstones of the world (2001)
DispersionNone
Walter Schumann, Gemstones of the world (2001)
Colour
Colour (General)All colours
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) Commonly bandedMore from other references
Causes of ColourPurple, microscopic sugilite inclusions. Purple, color center similar to that found in amethyst. Blue to greenish blue (chrysocolla quartz), microscopic to sub-microscopic inclusions. Green (chrysoprase), microscopic inclusions of nickeliferous clay-like material. Orange to red (carnelian, jasper), submicroscopic to microscopic inclusions of hydrous Fe oxides
W. William Hanneman, Pragmatic Spectroscopy For Gemologists (2011)
TransparencyTranslucent,Opaque
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) Semi-transparent to opaqueMore from other references
LustreWaxy
Michael O’Donoghue, Gems, Sixth Edition (2006)
More from other references
Fluorescence & other light emissions
Fluorescence (General)Often yellowish-green
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Crystallography of Chalcedony
Crystal SystemTrigonal
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
HabitFibrous to grained aggregate
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
More from other references
Geological Environment
Where found:Chalcedony is deposited in a variety of environments and deposition is commonly at low temperatures. Light-coloured material with no marked banding is often found as a late hydrothermal deposit or an alteration product in acidic to basic igneous rocks, tuffs and breccias. It is
vary common as crusts, as vein and cavity fillings.
Michael O’Donoghue, Gems, Sixth Edition (2006)
Spectrographic Data
Calculated Spectra:
Click spectra for more information
Chrysoprase - Locality: Unknown
Further Information
Mineral information:Chalcedony information at mindat.org
Significant Gem Localities
Czech Republic
 
  • Bohemia (Böhmen; Boehmen)
    • Hradec Králové Region
      • Jičín (Jitschin; Gitschin)
[var: Jasper] No reference listed
Madagascar
 
  • Mahajanga Province (Majunga)
    • Sofia Region
      • Analalava District
        • Ambolobozo
[var: Jasper] mindat.org
Morocco
 
  • Drâa-Tafilalet Region
    • Midelt Province
      • Upper Moulouya lead district
[var: Jasper] mindat.org
Myanmar
 
  • Mandalay Region (Mandalay Division)
    • Pyin-Oo-Lwin District
      • Mogok Township
        • Bernardmyo
          • Pyaung Gaung
[var: Chrysoprase] Ted Themelis (2008) Gems & mines of Mogok
[var: Chrysoprase] Ted Themelis (2008) Gems & mines of Mogok
        • Kyauk-Pyat-That
Ted Themelis (2008) Gems & mines of Mogok
Netherlands
 
  • Gelderland
[var: Jasper] mindat.org
Peru
 
  • Arequipa Department
    • Caraveli Province
[var: Chrysocolla Chalcedony]
  • Huancavelica Department
    • Huancavelica Province
      • Ascencion District
        • Yauricocha Parish
[var: Agate]
  • Huánuco Department
[var: Jasper]
  • Ica Department
    • Pisco Umay
[var: Chrysocolla Chalcedony]
  • Lima Department
    • Cañete Province
[var: Jasper]
  • Puno Department
[var: Jasper]
Poland
 
  • Lower Silesia (Dolnośląskie)
    • Ząbkowice District
[var: Chrysoprase] Gemstones of the world, Walter Schumann (2001)
Portugal
 
  • Beja District
    • Mértola
      • Alcaria Ruiva
[var: Jasper] mindat.org
Russia
 
  • Urals Region
    • Southern Urals
      • Orenburgskaya Oblast'
        • Orsk
[var: Jasper] Занимательная минералогия, Ферсман А., 1953, стр. 50
Sri Lanka
 
  • Sabaragamuwa Province
    • Ratnapura District
[var: Carnelian]
UK
 
  • Scotland
    • Tayside
      • Montrose
        • Usan
[var: Agate] [Specimen in the Natural History Museum, London]
USA
 
  • Arizona
    • Navajo Co.
[var: Petrified Wood] Gemstones of the world, Walter Schumann, 2001, p.148
        • Petrified Forest National Park
[var: Petrified Wood]
  • California
    • Imperial Co.
      • Jacumba Mts
        • Jacumba District
          • Boulder Park
U.S. Geological Survey, 2005, Mineral Resources Data System: U.S. Geological Survey, Reston, Virginia.
    • Inyo Co.
      • Amargosa Range
        • Black Mts
          • Jubilee Pass
[var: Jasper] Symons, Henry Heilbronner (1940), Quartz gem stones of California: Rocks & Minerals: 15: 41; Murdoch, Joseph & Robert W. Webb (1966), Minerals of California, Centennial Volume (1866-1966): California Division Mines & Geology Bulletin 189: 317.
    • Kern Co.
      • Kramer District (Kramer Borate District)
[var: Petrified Wood]
    • San Diego Co.
      • San Ysidro Mts
        • Dulzura
          • Southeast of Dulzura
Kunz, George Frederick (1906), Precious stones: Mineral Resources U.S., 1905: 1323-1358; Murdoch, Joseph & Robert W. Webb (1966), Minerals of California, Centennial Volume (1866-1966): California Division Mines & Geology Bulletin 189: 318.
    • Santa Clara Co.
      • Santa Cruz Mts
        • Paradise Valley
[Jasper var: Orbicular Jasper] Melhase, John (1934), A diversity of many fine minerals available in California for collectors: Oregon Mineralogist: 2(7): 7; Mineralogist, The (1935): 3(3): 34; Murdoch, Joseph & Robert W. Webb (1966), Minerals of California, Centennial Volume (1866-1966): California Division Mines & Geology Bulletin 189: 318; www.cst.cmich.edu/users/dietr1rv/jasper.htm
    • Siskiyou Co.
      • Cascade Range
        • Bogus Mountain
[var: Bloodstone] Symons, Henry Heilbronner (1940), Quartz gem stones of California: Rocks & Minerals: 15: 41; Murdoch, Joseph & Robert W. Webb (1966), Minerals of California, Centennial Volume (1866-1966): California Division Mines & Geology Bulletin 189: 318.
      • Klamath Mts
        • Cinnabar Camp
[var: Agate] U.S. Geological Survey, 2005, Mineral Resources Data System: U.S. Geological Survey, Reston, Virginia.
    • Tulare Co.
      • Ivanhoe
        • Venice Hills
[var: Chrysoprase] Tucker, W. Burling (1919), El Dorado, Lassen, Modoc, Tehama, and Tulare Counties: California Mining Bureau. Report 15: 911; MacFall (1951), Gem Hunter's Guide, 1st ed.; Goodwin, Joseph Grant (1958), Mines and mineral resources of Tulare County, California: California Journal of Mines and Geology (Report 54): 54(3): 344; Murdoch, Joseph & Robert W. Webb (1966), Minerals of California, Centennial Volume (1866-1966): California Division Mines & Geology Bulletin 189: 318; Pemberton, H. Earl (1983), Minerals of California; Van Nostrand Reinholt Press: 350, 424.
      • Tennessee Knob
[var: Chrysoprase] Kunz, George Frederick (1899), Precious stones: Mineral Resources U.S., 1898: 589; Tucker, W. Burling (1919), Tulare Counties: California Mining Bureau. Report 15: 911; Murdoch, Joseph & Robert W. Webb (1966), Minerals of California, Centennial Volume (1866-1966): California Division Mines & Geology Bulletin 189: 318.
  • Minnesota
    • Crow Wing Co.
[var: Binghamite] Gemstones of the world, W. Schumann, 2001, p. 204
  • Montana
    • Lewis and Clark Co.
      • East Helena
        • Eldorado Bar
E.Ya. Kievlenko (2003) Geology of gems, p. 70
  • Nevada
    • Humboldt Co.
      • Virgin Valley
[var: Petrified Wood] Gemstones of the world, Walter Schumann, 2001, p.148
  • Utah
    • Iron Co.
U.S. Geological Survey, 2005, Mineral Resources Data System: U.S. Geological Survey, Reston, Virginia.
    • Juab Co.
      • Thomas Range
        • Topaz Mountain
[var: Agate] U.S. Geological Survey, 2005, Mineral Resources Data System: U.S. Geological Survey, Reston, Virginia.
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