Zajacite-(Ce)
Encyclopedia
Zajacite or Zajacite- is a rare radioactive fluoride
mineral with formula: Na
(REE
xCa
1-x)(REEyCa1-y)F
6. REE means rare earth element
s mostly those belonging to the lanthanide
series. It crystallizes in the trigonal - rhombohedral system and has a white vitreous appearance with a conchoid
al fracture. It has a Mohs hardness of 3.5 and a specific gravity
of 4.44 to 4.55. Zajacite is transparent with refractive indices
of nω=1.483 and nε=1.503 and occurs as creamy to white grains and phenocryst
s in pegmatite
and aplite
pods or lenses in a peralkaline
igneous intrusion
.
It was discovered in 1993 at Strange Lake, Quebec
- Labrador
(56°20'N , 64°10'W) and was named for Dr. Ihor S. Zajac, who led the expedition responsible for its discovery, and who first recognized the presence of the new mineral.
Fluoride
Fluoride is the anion F−, the reduced form of fluorine when as an ion and when bonded to another element. Both organofluorine compounds and inorganic fluorine containing compounds are called fluorides. Fluoride, like other halides, is a monovalent ion . Its compounds often have properties that are...
mineral with formula: Na
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
(REE
Rare earth element
As defined by IUPAC, rare earth elements or rare earth metals are a set of seventeen chemical elements in the periodic table, specifically the fifteen lanthanides plus scandium and yttrium...
xCa
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
1-x)(REEyCa1-y)F
Fluorine
Fluorine is the chemical element with atomic number 9, represented by the symbol F. It is the lightest element of the halogen column of the periodic table and has a single stable isotope, fluorine-19. At standard pressure and temperature, fluorine is a pale yellow gas composed of diatomic...
6. REE means rare earth element
Rare earth element
As defined by IUPAC, rare earth elements or rare earth metals are a set of seventeen chemical elements in the periodic table, specifically the fifteen lanthanides plus scandium and yttrium...
s mostly those belonging to the lanthanide
Lanthanide
The lanthanide or lanthanoid series comprises the fifteen metallic chemical elements with atomic numbers 57 through 71, from lanthanum through lutetium...
series. It crystallizes in the trigonal - rhombohedral system and has a white vitreous appearance with a conchoid
Conchoid
Conchoid can refer to:*Conchoid curve, an equation discovered by the mathematician Nicomedes*Conchoidal fracture, a breakage pattern characteristic to certain glasses and crystals...
al fracture. It has a Mohs hardness of 3.5 and a specific gravity
Specific gravity
Specific gravity is the ratio of the density of a substance to the density of a reference substance. Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is nearly always water for...
of 4.44 to 4.55. Zajacite is transparent with refractive indices
Refractive index
In optics the refractive index or index of refraction of a substance or medium is a measure of the speed of light in that medium. It is expressed as a ratio of the speed of light in vacuum relative to that in the considered medium....
of nω=1.483 and nε=1.503 and occurs as creamy to white grains and phenocryst
Phenocryst
thumb|right|300px|[[Granite]]s often have large [[feldspar|feldspatic]] phenocrysts. This granite, from the [[Switzerland|Swiss]] side of the [[Mont Blanc]] massif, has large white [[plagioclase]] phenocrysts, [[triclinic]] [[mineral]]s that give [[trapezium|trapezoid]] shapes when cut through)...
s in pegmatite
Pegmatite
A pegmatite is a very crystalline, intrusive igneous rock composed of interlocking crystals usually larger than 2.5 cm in size; such rocks are referred to as pegmatitic....
and aplite
Aplite
Aplite in petrology, the name given to intrusive rock in which quartz and feldspar are the dominant minerals. Aplites are usually very fine-grained, white, grey or pinkish, and their constituents are visible only with the help of a magnifying lens...
pods or lenses in a peralkaline
Peralkaline
Peralkaline rocks include those igneous rocks which have a deficiency of aluminium such that sodium and potassium are in excess of that needed for feldspar. The presence of aegerine and riebeckite are indicative of peralkaline conditions....
igneous intrusion
Intrusion
An intrusion is liquid rock that forms under Earth's surface. Magma from under the surface is slowly pushed up from deep within the earth into any cracks or spaces it can find, sometimes pushing existing country rock out of the way, a process that can take millions of years. As the rock slowly...
.
It was discovered in 1993 at Strange Lake, Quebec
Quebec
Quebec or is a province in east-central Canada. It is the only Canadian province with a predominantly French-speaking population and the only one whose sole official language is French at the provincial level....
- Labrador
Labrador
Labrador is the distinct, northerly region of the Canadian province of Newfoundland and Labrador. It comprises the mainland portion of the province, separated from the island of Newfoundland by the Strait of Belle Isle...
(56°20'N , 64°10'W) and was named for Dr. Ihor S. Zajac, who led the expedition responsible for its discovery, and who first recognized the presence of the new mineral.