Sylvite
Synchysite-(Y) is a rare calcium yttrium cerium carbonate fluoride mineral. The mineral Synchysite is actually divided into three distinct minerals based on their respective dominant rare earth element; Synchysite-(Ce) with cerium, Synchysite-(Nd) with neodymium and Synchysite-(Y) with yttrium. Most Synchysite is Synchysite-(Y). Synchysite-(Y) occurs as translucent to opaque brownish-recl aggregates in association with Xenotime, Hematite, and Quartz.
Synchysite was originally discovered in 1894, but Synchysite-(Y) was discovered in 1951 at the Scrub Oaks iron Mine, Mine Hill, 4 km west of Dover, Morris County, New Jersey, USA. At that time it was thought to be a possible new yttrium fluorocarbonate mineral and was named Doverite after the nearby town. It was later determined to be a yttrium dominant variety of Synchysite and IMA approved in 1966. Synchysite-(Y) is named from the Greek word σύγχΰσις (synchys) meaning confounding in allusion to its initially being mistaken for Parisite, and the “-(Y)” suffix due to the dominance of yttrium in the composition. One of the main sources of Synchysite-(Y) is at the White Cloud pegmatite, South Platte district, Jefferson County, Colorado, USA.
Synchysite-(Y) distribution: in the USA, from the Scrub Oaks iron mine, Mine Hill, 4 km west of Dover, Morris Co., New Jersey; at the Henry pegmatite, near Cotopaxi, Fremont County, and the Big Bertha and White Cloud pegmatites, South Platte district, Jefferson County, Colorado; from Rib Mountain, Marathon County, Wisconsin. In the Evans-Lou quarry, near Wakefield, Quebec, Canada. Around Gallt y Wenallt, Gwynedd, Wales. On the west flank of Cherbadung [Pizzo Cervandone], Binntal, Valais, Switzerland. At Bad Grund, Harz Mountains, Germany. Crystallized in the Bantyshevo salt stock, Dnieper-Donets Basin, Ukraine. From the Jabal Sa’id pegmatite, central Saudi Arabia. At Xiaocaidan, Qinghai Province, China.
| Chemical Formula: | Ca(Y,Ce)(CO3)2F |
| Calcium Yttrium Cerium Carbonate Fluoride | |
| Molecular Weight: | 268.00 gm |
| Composition: | Calcium | 14.95 % | Ca | 20.92 % | CaO |
| Yttrium | 33.17 % | Y | 42.13 % | Y2O3 | |
| Carbon | 8.96 % | C | 32.84 % | CO2 | |
| Oxygen | 35.82 % | O | |||
| Fluorine | 7.09 % | F | 7.09 % | F | |
| — | — % | F | -2.98 % | -O=F2 | |
| 100.00 % | 100.00 % | = TOTAL OXIDE |
| Crystallography: | Monoclinic – Prismatic |
| Crystal Habit: | Crystals acute rhombohedral with small {0001}, or thick tabular {0001} and hemimorphic (ditrigonal-pyramidal). {0001} smooth and brilliant; lateral faces striated horizontally; crystals to 0.2 mm; typically in very fine-grained aggregates. |
| Twinning: | On {0001} common also lamellar |
| Cleavage: | Parting on {0001} |
| Fracture: | Splintery, sub-conchoidal |
| Tenacity: | Brittle |
| Moh’s Hardness: | ~4.5 |
| Density: | 3.90 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioactive |
| Other: | Rather easily soluble in acids. |
| Color: | Red-brown, pale yellow, pale pink, colorless |
| Transparency: | Transparent to translucent, opaque |
| Luster: | Sub-adamantine, vitreous, greasy |
| Refractive Index: | 1.643 – 1.740 Uniaxial ( + ) |
| Birefringence: | 0.077 |
| Dispersion: | Relatively strong |
| Pleochroism: | Weak; absorption E greater than O |
