ユージアル石 (Eudialyte)


研磨されたユージアル石 0.08 - 2.28ct
(Polished and faceted Eudialyte)

0.17ct 3.2x2.8mm 0.36ct 5.6x3.9mm 0.47ct 6.0x4.0mm 2.28ct 9.0x7.0mm
Sheffield Lake Kipawa River Kipawa Basin
Quebec, Canada

  Ø2.3mm 0.08ct. ea. 研磨されたユージアル石 9x7cm
Lovozero, Khibiny, Kola Peninsular, Russia


Eudialyte(reddish orange)
with albite(white) 2- 3ct
宝石質部を含む結晶 49x27mm
Eudialyte with gemmy crystal
magnified view
ユージアル石結晶 1.5mm
Eudialyte crystal 1.5mm
Horváth collection
Kipawa Basin Mont Saint Hilaire
Quebec, Canada
Eudialyte crystal(8mm) in Agrellite: NaCa2[F/Si4O10](50mm)
Kipawa Basin, Quebec, Canada
Agrellite shwon under
short wave UV(235nm)
Eudialyte crystal 5x4x3cm
Nanjakasik, Ilimasauq, Greenland
Norra Kärr, Sweden
Jungni Hill, Malawi

ユージアル石を含む母岩 Grännaite
Eudialyte is discovered as red
phenocryst in rock called Grännaite
Bright red Eudialyte
Eudialyte cabochon with white
albite and black arfvedsonite
Norra Kärr alkaline complex, Sweden
化学組成(Composition) Na15Ca7,Fe3Zr3Si[Cl/Si3O9/Si9O27/(OH,Cl)]
結晶系(Crystal system) 三方晶系 (Trigonal)
結晶形(Crystal Form )
モース硬度 (Hardness) 5 - 6
比重(Density) 2.60 - 3.10
屈折率(Refractive Index) 1.599-602

名前について (About name)
 ロシアの鉱物学者、A・フェルスマンの名著 ”石の思い出”(理論社 1956年刊行、永らく絶版となっていましたが、2005年、多少内容を変えて復刊)を読まれた方は、”ツンドラ一面に飛び散ったラップランド人の血の石,ヒビ−ヌイ山地にある際だって赤い鉱物、ユージアル石 ・・・” を憶えていることでしょう。 実に半世紀近くもの期間、それがどんな鉱物なのか、ただ思いを巡らすのみでありました。

 Eudialyte is named after Greek "Eu : well and Dialusis : soluble" for it's solubility in acids.
In spite of its rarity, eudialyte is well memorized by mineral collectors for poetic descriptions in " Reminiscenses about Minerals" written by Russian mineralogist, A.E. Fersman. It took almost half century until we could see what is eudialyte, the extreme vermillion colored mineral, like Lapp's blood. Specimens of eudialyte appeared in mineral market recently, although as scarece specimen yet.

産地と産状 (Origin and Occurence)

 最近の研究ではユージアル石は単独ではなくその大半が稀な種類の広範な鉱物群の一つであるとされています。現在分かっているだけでも ; alluaivite, aqualite, carbokentbrooksite, eudialyte, feklichevite, labyringhite, manganokhomyakovite, oneillite, raslakite, rastsvetaevite, sirsillite-(Ce), tasequite, ・・・・まだまだ続くのですが、いずれも上記の化学組成の元素を共通に、しかし少しずつ異なる割合で含むグループです。

 Eudialyte occurs mostly in so-called alcaline intrusions, rich in aluminium and zirconium, particularly in nephline syenites and their pegmatites. It was first discovered near Narsaq in Western Greenland. Eudialyte is fairly abundant as a rock-forming mineral in the alkaline complexes of Lovozero and khibinyi in the Kola Peninsular, Russia and of Langensundsfjord, Norway. It also occurs in Guinea, Madagascar、South Africa and in U.S.A. Kipawa Basin, Quebec, Canada is known for gemmy crystals.
 Eudialyte is potentially a zirconium ore. Russia, who has not any major deposits of accessible zirconium, had extensively explored the Kola Penisula. Zirconium alloys are used to encapsulate fuel rods in nuclear reactors ; zirconium lets nutron pass, which is an essential factor that nuclear fission reaction starts.
Do you notice that chemical formula in the box is quite complex ? But this is simplifed one, yet. It always took a very tolerant view to consider eudialyte a single mineral, and the term "eucolite" has been used for calcium-rich eudialyte.
The specific gravity varies within about +/- 10%, birefringence is positive or negative, and chmical composition is all over the place! Recent research has proven that eudialyte is not just eudialyte but an entire group of minerals, most of which are rare. Currently the eudialyte group includes the approved species ; alluavite, aqualite, carbokentbrookside, eudialyte, feklichevite, labyrinthite, manganokhomyakite, oneillite, raslakite, rastsvetaevite, zirsilite-(Ce). And more are coming ! Colors are ; brown, reddish brown, bright red, yellow, even green or purple.

宝石質のユージアル石 (Gem quality eudialyte)


 Most of eudialyte crystals are opaque and rarely shows crystal form. Quite rarely, facetted or cabochon cut stones appear in the market.
Left photo in 4th low from top shows free cabochon cut stones, collected as much as 45kg of gemmy crystals in 1999. Almost all gemmy crystals are collected from Quebec, Canada, once for
every 5 year and the biggest stone is as small as less than 0.5ct.
 Faceted eudialyte from Lovozero, Kola Peninsular, Russia is quite rare. Although extremely small, this is the first faceted stone, I have ever seen from this locality.


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