Strontium aragonite with

Another excellent quantitative worker, who also (like Klaproth) made many analyses of minerals, was Friedrich Stromeyer (Gottingen 2 August 1776-18 August 1835), a pupil of Vauquelin who first studied botany. He became professor of chemistry in Gottingen in 1810. He wrote books on chemistry and published a number of important investigations. He showed that aragonite is a definite crystalline form of calcium carbonate and is not necessarily contaminated with strontium, and recommended starch as a reagent for free... 

Strontium Carbonate. Strontium carbonate, SrCO, occurs naturally as strontianite in orthorhombic crystals and as isomorphs with aragonite, CaCO, and witherite, BaCO. There are deposits in the United States in Schoharie County, New York in WestphaUa, Germany and smaller deposits in many other areas. None is economically workable. Strontianite has a specific gravity of 3.7, a Mohs hardness of 3.5, and it is colorless, gray, or reddish in color. 

Unfortunately, there is generally a large scatter in the values obtained for these partition coefficients. A possible reason for this scatter, as shown by the study of Lorens (1981), is probably the major effect of precipitation rate on the values of the partition coefficients. It is interesting to note that the partition coefficients for the transition and heavy metals in calcite, studied by Lorens (Cd2+, Mn2+, Co2+), have a negative linear log partition coefficient- log precipitation rate relation, whereas Sr2+ has a positive relation. This behavior may be explained by the fact that the transition metal carbonates are isostructural with calcite, whereas strontium carbonate is isostructural with aragonite. Also, as precipitation rates increase, partition coefficients tend towards unity. 

Figure 7.39. Schematic diagram illustrating the effects of climate on meteoric diagenetic pathways for coeval carbonates originally composed of a polymineralic assemblage of calcite with various amounts of magnesium and strontium-rich aragonite. (After James and Choquette, 1984.)...

Sr/ Sr ratios in several samples of glacial runoff in the Himalayas are consistent with carbonate being the main source of calcium and strontium, but Ca/Sr ratios are relatively low. This suggests that these waters may precipitate calcite or aragonite when they warm (Jacobson et al., 2002). 

Some substitution of strontium (up to 14 mol.%), of lead (2 mol.% reported) but no barium has been reported in aragonite, although investigations at elevated temperatures and pressures show almost complete miscibility of these elements in the structure (Gaines et al., 1997, p. 442), and SrCOs (strontionite), BaCOs (witherite), and PbCOs (cerussite) are common minerals. A calculated plot (Figure 3(b)) for cations in ninefold coordination shows that this coordination theoretically allows trivalent rare earth elements and quadravalent and many other elements to be substituents in the structure. Ytterbium, europium, samarium, and radium carbonates with aragonite structure have been synthesized (Spear, 1983). 

Comment. Gott., 1811-13, Ann. Chim., 1814, xcii, 254 . Chem. (Schweigger), 1815, xiii, 362 (with Hausmann), 490 Laugier, J. des Mines, 1814, xxxvi, 313 id., Ann. desMines, 1818, iii, 113 Dobereiner, J. Chem. Phys., 1814, x, 217 and Bucholz and Meissner, J. Chem. Phys., 1815, xiii, I, all found that aragonite may be almost or quite free from strontium. 

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