Russian Gemstones Encyclopedia

Vladimir Bukanov. Russian Gemstones Encyclopedia



MONAZITE (Monazit—Monazite—ћонацит) (Breithaupt, A. 1829), from Gk. “monazein” – to be solitary, after its rare occurrence to be an isolated crystal in the mineral material.

Composition & Properties. Phosphate – Ce[PO4], monoclinic system. Hardness 5-5.5. Density 4.6-5.4. Pitch luster to diamond one. Cleavage in one-two directions, there is separateness. Fragile. Radioactive. Monazite is represented mainly with small flattened crystals and grained aggregates. Color: reddish-brownish to brownish, yellow, greenish or white. Transparent to translucent. Sometimes, it displays the alexandrite effect. In the daylight it is yellow-orange, in the electric light it is reddish-orange, and in ultra-violet rays it is light green. Such color can be displayed in the case of the absence of admixtures of thorium, uranium, iron, and with the content of Nd2O3 not more than 16%. Pale tones are produced by admixtures of rare-earth elements. Because of admixtures of thorium, monazite is radioactive.

Deposits. Monazite is found at magmatic, metasomatic and metamorphic deposits and in pegmatites. It is accumulated in significant volumes on placers. In Russia, findings of monazite crystals are known in the north of Karelia, in pegmatites of Chërnaya Salma, in the region of Chupa. In the Subpolar Urals Mts., transparent crystals of pale yellow monazite, not more than 1 cm., are found in alpine veins together with rock crystal. In the Middle Urals, monazite was discovered in pegmatites of the Semenihinskaya mine, near Adui; and in the South Urals – in the Kosaya Mt. in the Ilmeny Mts. In Central Kazakhstan, at the Bektau Ata deposit, they found large crystals of monazite. In the southern part of Norway crystals of monazite at the deposits Arendal and Moss, Østfold, were found. In Switzerland, in alpine veins monazite is represented with transparent crystals up to 1 cm.; there it is known as turnerite, e.g. at Binntal, Valais canton. In Romania red crystals monazite up to 20 cm. occurs in alkaline rocks at Ditrâu, East Carpatian Mts. In Mozambique, at the Muiane deposit, in the Alto Ligonha Region, they found crystals of monazite up to 10 cm. long. On Madagascar, at the Ambatofotsikely deposit, near Miandrarivo, they found transparent crystals of monazite; at the Madiombi Nord deposit their size reached 7x5x2.5 cm.; and in the south of the island, large crystals were found at the Ihosy deposit. Gem-quality, gravel crystals of monazite were found on placers of Sri Lanka. In Southern Australia large crystals of monazite, together with taaffeit, were discovered at the Mt. Painter deposit. In Canada, near the border with Newfoundland in Québec, at the Strange Lake deposit, in pegmatite they discovered large crystals of monazite. In the U.S.A., in North Carolina, they found monazite crystals up to 26x23x16 cm. and to 25 kg. at the deposits Mars Hill, Madison Co., also and Stony Point, Alexander Co. They were sometimes with transparent segments, available for faceting, which displayed the alexandrite effect. In Virginia, in pegmatite at the Amelia Court House deposit, Amelia Co., they found monazite crystals up to 15x5 cm. in size; also in California, they made faceted stones up to 0.6 ct. from monazite crystals of the Riverside deposit. In Connecticut large transparent monazite crystals were discovered at the Norwich deposit, New London Co. In Brazil, they found monazite crystals up to 20 cm. long, with transparent segments at the Jaguaraçú deposit, near Teophilo Otoni, Minas Gerais,.

Synonyms. Edwardsite | Eremite | Urdit, after the Urda deposit, in Norway.

Cut Gems. Monazite in the faceted form is usually not more than 5 ct.; in cabochons it can be rather bigger. However, because of its possible radioactivity it is of collection interest only.

Similarity. Monazite looks like chondrodite, clinohumite, hessonite, spessartine and zircon.