Eudialyte

Infobox mineral
name = Eudialyte
category =
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caption =
formula = sodium₁₅calcium₆(iron,manganese)₃ zirconium₃siliconoxygen(oxygen,hydroxide,hydrogen₂oxygen)₃(silicon₃oxygen₉)₂(silicon₉oxygen₂₇)₂ (hydroxide,chlorine)₂
molweight =
color = Red, magenta, brown; also blue and yellow
habit = Granular, tabular
system = Trigonal
twinning =
cleavage = [0001] Imperfect
fracture = Uneven
mohs = 5 - 5.5
luster = Vitreous
refractive = 1.598 - 1.602
opticalprop =
birefringence =
pleochroism = Weak, brown-red to red-pink to yellow
streak = White
gravity = 2.8 - 3
melt =
fusibility =
diagnostic =
solubility = H₂SO₄
diaphaneity = Transparent to translucent
other =

Eudialyte, whose name derives from the Greek "eu" and "dialytos", meaning "well decomposable", is a somewhat rare, red silicate mineral, which forms in alkaline igneous rocks, such as nepheline syenites. Its name alludes to its ready solubility in acid.

Uses of eudialyte

Eudialyte is used as a minor ore of zirconium. Another use of eudialyte is as a minor gemstone, but this use is limited by its rarity, which is compounded by its poor crystal habit. These factors make eudialyte of primary interest as a collector's mineral.

Associated minerals

Eudialyte is found associated with other alkalic igneous minerals, in addition to the some minerals common to most igneous material in general. These minerals include:
*nepheline, (sodium, potassium)aluminumsiliconoxygen₄
*aegirine, sodiumironsilicon₂oxygen₆
*natrolite, sodium₂aluminum₂silicon₃oxygen₁₀hydrate|2
*albite, sodiumaluminumsilicon₃oxygen₈

Alternative names

Alternative names of eudialyte include: almandine spar and eudalite. Eucolite is the name of an altered form.

Notes for identification

Eudialyte's rarity makes locality useful in its identification. Prominent localities of eudialyte include Mont Saint-Hilaire in Canada and the Kola Peninsula in Russia, but it is also found in Greenland, Norway, and Arkansas. The lack of crystal habit, associated with color, is also useful for identification, as are associated minerals. A pink-red mineral with no good crystals associated with other alkaline igneous material, especially nepheline and aegirine, is a good indication a specimen is eudialyte.

Eudialyte group

Microchemical (by electron microprobe) and structural analyzes of different eudialyte (and related) samples revealed presence of many new eudialyte-like minerals. These minerals are structurally and chemically related and joined into eudialyte group. The group includes Zr-,OH-, Cl-, F-, CO₃- and possibly also SO₄-bearing silicates of Na, K, H₃O, Ca, Sr, REEs, Mn, Fe, Nb and W. Electron vacancies can be present in their structure, too.

References

* [http://www.webmineral.com/data/Eudialyte.shtml WebMineral Listing]
* [http://www.mindat.org/min-1420.html MinDat Listing]
* [http://mineral.galleries.com/minerals/silicate/eudialyt/eudialyt.htm Mineral Galleries]