Morton[94] states that he prepared a crystalline didymium carbonate in the laboratory, of the formula Di₂(CO₃)₃,8H₂O, which was isomorphous with lanthanite; he concluded that the latter had only eight instead of nine molecules of water.
[94] See abstract in Zeitsch. Kryst. Min. 1886-87, 12, 518.
Parisite (Synchisite), and Cordylite.
—Parisite is a fluocarbonate of calcium and cerium metals; Cordylite is an analogous compound in which barium replaces calcium, and is isomorphous with Parisite. The formula of Parisite is CaR₂F₂(CO₃)₃, where R = cerium metals. Groth formulates this as (CaF)(RF)R(CO₃)₃, Penfield and Warren as (RF)₂Ca(CO₃)₃, whilst Schilling gives Ce₂(CO₃)₃,CaF₂. Analogous formulæ may be proposed for Cordylite, BaR₂F₂(CO₃)₃. Since the two minerals are very similar in crystallographic properties, one description will be sufficient for both. The following are Dana’s data for Parisite:
Hexagonal, c = 3·2891. (0001) ∧ (101̅1) = 75° 15´.
Forms are extremely numerous, and have remarkably high indices. Among the simplest are the base c {0001}, the prism m {101̅0}, pyramids q {101̅2}, and h {112̅2}; the other forms are chiefly rhombohedra and pyramids. The usual habit is that of an acute double hexagonal pyramid, with form o {202̅1}, terminated by c. Cleavage ∥ c, perfect.
It is brownish-yellow to red. Hardness 41⁄2; sp. gr. 4·36.
The double refraction is strong, positive. Soluble in hydrochloric acid with effervescence.
Both minerals are characteristic pneumatolytic species of the riebeckite-ægirine rocks. Parisite was discovered by Paris in the emerald mines of the Muso valley, Colombia, in 1835, and first correctly analysed by Bunsen in 1845. Before the blowpipe it glows, remaining infusible (the glow does not appear to have been investigated in this case).
Cordylite was discovered by Flink in 1900, in Greenland.