Home Gemstone Zircon

Zircon

SHARE

Zircon is a zirconium silicate mineral with a chemical composition of ZrSiO4. It is common at some point of the world as a minor constituent of igneous, metamorphic, and sedimentary rocks. It is a popular gemstone that has been used for almost 2000 years. It takes place in a huge range of colours and has a brightness and hearth that competitors those of diamond. Colorless zircon is now and again used as a lower-price opportunity for diamond. Zircon must no longer be harassed with cubic zirconia, that’s a man-made cloth.

Name: Thought to be derived from the Persian zar, for gold, and gun, for color, through the Arabic zarqun.

Association: Feldspars, amphiboles, mica, quartz.

Crystallography: Tetragonal; ditetragonal-dipyramidal. Crystals usually show a simple combination of prism and dipyramid of the first order. The prism of the second order and a ditet­ragonal dipyramid also observed. Base very rare. Usually in crystals; also in irregular grains.

Zircon Composition: Zirconium silicate, ZrSi04. Zr02 = 67.2 per cent, Si02 = 32.8 per cent.

Diagnostic Features: Recognized usually by its characteristic crystals, color, luster, hardness, and high specific gravity.

Similar Species: Thorite, ThSi04, is like zircon in form and structure; usually hydrated and black in color

Occurrence

It is a common accessory to hint mineral constituent of most granite and felsic igneous rocks. Due to its hardness, sturdiness and chemical inertness, zircon persists in sedimentary deposits and is a not unusual constituent of most sands. It is uncommon within mafic rocks and very rare within ultramafic rocks other than a collection of ultrapotassic intrusive rocks which includes kimberlites, carbonatites, and lamprophyre, where zircon can on occasion be determined as a trace mineral as a result of the unusual magma genesis of those rocks.

Physical Properties of Zircon

Chemical ClassificationSilicate
ColorUsually yellow, brown, or red. Also colorless, gray, blue, and green.
StreakColorless. Usually harder than the streak plate.
LusterVitreous to adamantine, sometimes oily.
DiaphaneityTranslucent to transparent
CleavageImperfect
Mohs Hardness7.5
Specific Gravity4.6 to 4.7
Diagnostic PropertiesHardness, luster, specific gravity
Chemical CompositionZrSiO4
Crystal SystemTetragonal
UsesOre of zirconium metal, ore of zirconium dioxide, whitening agents, white pigment, gemstones, radiometric dating.

It is ubiquitous inside the crust of Earth. It happens as a not unusual accent mineral in igneous rocks (as primary crystallization merchandise), in metamorphic rocks and as detrital grains in sedimentary rocks. Large zircon crystals are uncommon. Their common size in granite rocks is ready zero.1–zero.Three mm, but they also can grow to sizes of several centimeters, in particular in mafic pegmatites and carbonatites. It is likewise very proof against warmth and corrosion.

Because in their uranium and thorium content, a few zircons go through metamictization. Connected to inner radiation harm, those techniques in part disrupt the crystal shape and in part provide an explanation for the noticeably variable residences of zircon. As zircon will become increasingly modified by means of internal radiation harm, the density decreases, the crystal structure is compromised, and the colour changes

Zircon Optical Properties

Euhedral zircon grain within a granitic gneiss. Note the highly fractured nature of the grain and the very strong relief. PPL
The same image as that on the left, the high interference colours of the zircon grain are not readily evident in this image,
XPL
PropertyValue
FormulaZrSiO4
Crystal SystemTetragonal  (4/m2/m2/m)
Crystal HabitMicroscopic crystals
CleavagePoor {110} prismatic,  Poor {111} pyramidal
Hardness7.5
StreakWhite
Specific Gravity4.68
Color/PleochroismGrayish, yellowish, or reddish brown. Also may be colorless, yellow, gray, pink, or blue-green. Colorless to pale brown in thin section.
FluorescenceThermoluminesecent, cathodoluminescent, may fluoresce under UV light
Optic SignUniaxial (+)
2Vnot usually observed due to small crystal size
Optic Orientationlength slow
Refractive Indices
omega =
epsilon =
1.920 – 1.960 (1.924 – 1.934, natural non-metamict)1.967 – 2.015 (1.970 – 1.977)
Max Birefringence0.036 – 0.0650.036 – 0.053 (natural non-metamict)
Elongationalong C-axis
Extinctionparallel in longitudinal or in grain mount
Distinguishing FeaturesIt is not usuall seen in hand sample; when it is, it may be distinguished by crystal habit and hardness.In thin section, It is found in the form of small crystals included in other minerals, showing very high relief and high-order interference colors. Distinctive dark halos formed by radioactive decay may  be present when its is included in minerals such as biotite, hornblende, or cordierite.
EditorsCassie Stearns (06), Sarah Brisson (’14) ( Smith.edu, 2019)

Zircon Mining

zircon concentrate production

It has been mined from flow gravels for over 2000 years. This early mining of zircon was mainly to achieve high-quality crystals for use as gems. Today, maximum zircon is produced with the aid of mining or dredging zircon-rich sediments. These sediments can be in seashore, littoral, or alluvial deposits.

Zircon Uses

Industrial Uses

  • Zircon sand has a low enlargement coefficient and may be very stable at high temperatures. It is used as a refractory cloth in many foundry and casting applications. One of its maximum common uses is inside the manufacturing of ceramics.
  • Zirconium dioxide (zirconia) is produced by using heating zircon sand to a excessive enough temperature to break down the zircon molecule. In powdered form, zirconium dioxide is vibrant white, exceedingly reflective and thermally stable. It is used as an opacifier, whitening agent, and pigment in glazes and stains used on ceramics and pottery. Yttria-stabilized zirconia is used to fabricate cubic zirconia, fiber optic additives, refractory coatings, ceramics, dentures and other dental merchandise.

Zircon as a Gemstone

  • It has been used as a gemstone for over 2000 years. Its very high dispersion and refractive index supply it a brilliance and fire that rival those of diamond. For that reason, colorless faceted zircon has been used as each a popular and fraudulent substitute for diamond.

Zircon and Radioactive Decay

  • Many zircon crystals includes trace amounts of uranium and thorium. These radioactive factors had been incorporated into the zircon on the time of crystallization. They convert into their decay products at a constant fee. The ratio of determine substances to daughter products can be used to estimate the time of crystallization. Using this technique, the oldest mineral grains inside the global are zircon crystals discovered in Australia. They are estimated to be about 4.Four billion years old.

Distribution

An unusually common and widely distributed mineral, but fine crystals are rare.

  • In Norway, at Larvik and Hakedal; on Seiland Island, Alta River, Finnmark.
  • At SillinjÄarvi, Finland.
  • From Sibnitz, Saxony, Germany.
  • At Miass, Ilmen Mountains, Southern Ural Mountains, Russia.
  • In the USA, at Deer Hill, Orange Co., and Fine, St. Lawrence Co., New York; from near Franklin, Sussex Co., New Jersey; near Green River, Henderson Co., North Carolina; at Tigerville, Greenville Co., South Carolina; and from Cheyenne Mountain and St. Peters Dome, near Pikes Peak, El Paso Co., Colorado.
  • On Turner’s Island, in Lake Clear, and at Kuehl Lake, Renfrew Co., Ontario, Canada.
  • In the Matura and Saragam districts, Sri Lanka.
  • From Mt. Ampanobe, near Fianarantsoa, and Itrongahy, near Betroka, Madagascar.
  • At Teete, Mozambique.
  • Large crystals from Mud Tank, Valley Bore, Northern Territory, Australia.

References

  • Dana, J. D. (1864). Manual of Mineralogy… Wiley.
  • Handbookofmineralogy.org. (2019). Handbook of Mineralogy. [online] Available at: http://www.handbookofmineralogy.org [Accessed 4 Mar. 2019].
  • Mindat.org. (2019): Mineral information, data and localities.. [online] Available at: https://www.mindat.org/ [Accessed. 2019].
  • Smith.edu. (2019). Geosciences | Smith College. [online] Available at: https://www.smith.edu/academics/geosciences [Accessed 15 Mar. 2019].
Cite this article as: Geology Science. (2019). Zircon. [online] Available at: http://geologyscience.com/minerals/zircon/ [8th December 2019 ]
SHARE