Russian Gemstones Encyclopedia

Vladimir Bukanov. Russian Gemstones Encyclopedia



EUDIALYTE (Eudialyt—Eudialyte—Ёвдиалит) (Sromeyer, F. 1819), from Gk. “eu” – well and “dialytos” – dissolved, alluding to its easy solubility in acids.

Composition & Properties. Silicate – (Na14Ca)Ca6Fe32+•Zr3[Cl,OH)2|(Si3O9)2|•(Si9O27•SiO)2]. subclasses ring silicate. Trigonal system. Hardness 5.5. Density 2.7-3.1. Glass luster. Fragile. Grained aggregates of eudialyte form massive accumulations in bedding rock. Their spread reaches several meters with the thickness up to 1 m. Sometimes, eudialyte is represented with thick-plate, columnar and isometric crystals. Rarely, it is transparent, more often – half-transparent to translucent. Color: rose to raspberry-red and yellow-brown, which depends on the correlation between the admixtures of manganese (Mn3+) and iron (Fe3+). Eudialyte in alkali pegmatites can be founded in the form of crystals up to 10 cm. in cross-section, and sometimes even more. A transparent brown-red jewelry-ornamental variety is called eucolite.

Deposits. Eudialyte is widespread in nepheline syenites, alkali massifs and pegmatites linked with them. Grained aggregates of eudialyte form massive accumulation up to several meters long, with the thickness not more than 1 m. In alkali pegmatites eudialyte is represented with half-transparent to translucent table, columnar and isometric crystals. Their size reaches 8x3.5 cm., but transparent crystals are not more than 1 cm. It has been known since the end of the 18th cent. as “red sheet-like garnet from Greenland”. In 1847, eudialyte was discovered in Norway. In Russia, it was discovered in Khibiny and in Lovozero massif in 1893. In his popular editions A.E. Fersman’s called red spots of eudialyte Saamy blood. For an isotropic difference of eudialyte they offered the name mesodialyte, and eudialyte with the piezoelectric effect they described at first as a new mineral barsanovite. In Khibiny, in the Nyorkpakhk Mt., there resources of eudialytite were valued as those of an ornamental stone. There also translucent crystals of eudialyte up to 7x5x4 cm. were found. Beside eudialytite, in the Khibiny massif there are nepheline syenites with ornamental properties – they contain less eudialyte: chibinite with lujavrite and close to them eudialyte urtite. Chibinite consists of microcline on 40-45%, from nepheline, aegirine and eudialyte on 35-45%. In eudialyte-lujavrite the content of nepheline is not less than 30%, microcline – not more than 25%, aegirine – 40-80%, eudialyte – 10-30%. Isolations of eudialyte in this rock reached the size of 10x10x15 cm. In the Krasnoyarsk Region eudialyte was discovered in alkali granites in the Talnakhskiy massif, by Noril’sk; at East Sayan Mts. – Aliberovskiy mine; and in Tyva. In the western part of the Chukchi Penin., it was discovered in the Amandykanskiy massif, in the basin of the Omolon River.

In South Kyrgyzstan, eudialyte was discovered in the Khodja Achkan massif, in the Alayskiy Range, in the region of Khaydarken. In Tadzhikistan, it was described in the alkali massif Dara-i-Pioz, in the Alai Mts. For the first time, eudialyte was discovered in South-western Greenland, Denmark, in the Ilimaussaq alkali massif, where it existed as crystals, 4x2 cm. in size, at the Fiskenaesset deposit. Besides, there it contained as rock-forming mineral in nepheline syenite – kakortokite. In Norway, at the Langesund deposit, Telemark, they found a transparent variety of deep-brown eudialyte – eucolite; which is found out also in Sweden, at the Norra Karr deposit, near Gräuna; and in Ireland, at the Carlingford deposit, near Dundalk. Among the other countries of Europe, eudialyte was found in alkali massifs of Northern Ireland and Sweden, In Africa, eudialyte is known in Namibia, South Africa and on Madagascar. In Canada, crystals eudialyte up to5 cm. was discovered at the Mont St Hilaire of alkali rocks. There were also findings of this mineral even in The U.S.A., Guinea and Antarctic.

Synonyms. Barsanovite | Lopary blood (saamy blood) after the syn. Saamy – Lopary, used for his description of Finno-Ugric people lived on the Kola Penin., Russia | Greenland hyacinth | Kakortokite, after the discovery location near Yulianehoba (the Eskimo name is Kakartok), Greenland | Almandine spar | Greenland spar.

Treatment. Because of its non-transparency, it is processed mainly in cabochons. It resembles almandine in color. From transparent brown-red variety – eucolite they receive faceted stones up to 0.25 ct. As an ornamental stone they use eudialyte-containing nepheline syenites: eudialytite, kakortokite and others. They are used in stone-carving, for manufacturing of candlesticks, ash-trays, balls and different souvenirs.