Sixth stream elements are Sodium, Scandium(Titanium), Zirconium(Ruthenium) and Tungsten(Radium).

Occurrence of SodiumEdit

Mineral Albita GDFL039

Albite (NaAlSi3O8), a sodium-containing mineral.

Owing to its high reactivity, sodium is found in nature only as a compound and never as the free element. Sodium makes up about 2.6% by weight of the Earth's crust, making it the sixth most abundant element overall[1] and the most abundant alkali metal. Sodium is found in many different minerals, of which the most common is ordinary salt (sodium chloride), which occurs in vast quantities dissolved in seawater, as well as in solid deposits (halite). Others include amphibole, cryolite(Na3AlF6, sodium hexafluoroaluminate) , soda niter and zeolite(Na2Al2Si3O10-2H2O, the formula for natrolite).

Sodium is relatively abundant in stars and the D spectral lines of this element are among the most prominent in star light. Though elemental sodium has a rather high vaporization temperature, its relatively high abundance and very intense spectral lines have allowed its presence to be detected by ground telescopes and confirmed by spacecraft (Mariner 10 and MESSENGER) in the thin atmosphere of the planet Mercury.[2]

Occurrence of ScandiumEdit

Scandium does not have a particularly low abundance in the earth's crust. Estimates vary from 18 to 25 ppm, which is comparable to the abundance of cobalt (20–30 ppm). However, scandium is distributed sparsely and occurs in trace amounts in many minerals.[3] Rare minerals from Scandinavia[4] and Madagascar[5] such as thortveitite(scandium yttrium silicate (Sc,Y)2Si2O7), euxenite( (Y,Ca,Ce,U,Th)(Nb,Ta,Ti)2O6), and gadolinite ((Ce,La,Nd,Y)2FeBe2Si2O10)are the only known concentrated sources of this element. Thortveitite can contain up to 45%, as scandium(III) oxide.[4]

Scandium is more common in the sun and certain stars than on Earth. Scandium is only the 50th most common element on earth (35th most abundant in the Earth's crust), but it is the 23rd most common element in the sun.[6]


  1. Lide, D. R., ed. (2005), CRC Handbook of Chemistry and Physics (86th ed.), Boca Raton (FL): CRC Press, ISBN 0-8493-0486-5 
  2. "Sodium found in Mercury's atmosphere". BNET (1985-08-17). Archived from the original on 2012-07-08. Retrieved on 2008-09-18.
  3. Bernhard, F. (2001). "Scandium mineralization associated with hydrothermal lazurite-quartz veins in the Lower Austroalpie Grobgneis complex, East Alps, Austria". Mineral Deposits in the Beginning of the 21st Century. Lisse: Balkema. ISBN 9026518463. 
  4. 4.0 4.1 Kristiansen, Roy (2003). "Scandium - Mineraler I Norge" (in Norwegian). Stein: 14–23, 
  5. von Knorring, O.; Condliffe, E. (1987). "Mineralized pegmatites in Africa". Geological Journal 22: 253. doi:10.1002/gj.3350220619. 
  6. Lide, David R. (2004). CRC Handbook of Chemistry and Physics. Boca Raton: CRC Press. pp. 4–28. ISBN 9780849304859.