SYNCHYSITE FROM NORWAY
by Ronald Werner
In most collections abroad Synchysite-(Ce) will be represented by specimens from Alpine localities, Mt. St.-Hilaire (Canada) or in exceptional cases maybe even from Narssârssuk at Greenland. Synchysite from norwegian localities will most likely be absent. For whatever reason, this is undoubtedly not because Norway hasn`t got it`s own share of excellent localities for this interesting and attractive mineral.
The name "Synchysite" comes from the Greek word for "exchange" in the sense of a confusion concerning identity. Synchysite was first discovered in the famous Narssarsuk pegmatite at Greenland, but not recognized as such, and was mistakingly held for the already known and described mineral "parisite". Both Gustav Nordenskiold (1869-1928) and Gustav Flink (1849-1932) reported about this find. In a later publication Flink came to the conclusion that the concerned material should represent a new species. After a new description of the original parisite, Flink gave the mineral it`s present name: synchysite. In 1953 the American scientists G. Donnay & J.D.H.Donnay solved the problem once and for good. They discovered the existance of no less than 4 cerium-fluor-carbonates: bastnäsite, parisite, röntgenite and synchysite. In most cases these minerals occur as a polycrystal of 2 or more of these 4 species. Crystals containing only 1 of the 4 minerals are less common. However, often is the syntaxy of the minor member in the dominant phase only present on a micron-scale or sub-micron-scale. In those cases it is very difficult (expensive) to determine the presence of the sub-ordinate phase. To what extent supposedly pure synchysite-crystals also contain another phase is therefore in most casesunknown.The synchysite occurring in Norway contains cerium as the dominant REE, and should according to the international I.M.A./C.N.M.M.N. nomenclature be called "synchysite-(Ce)". From occurrences abroad synchysite with dominance of Neodymium and of Yttrium are known, respectively synchysite-(Nd) and synchysite-(Y) (doverite).
crystal-form: orthorhombic, pseudo-hexagonal
crystal-habits: thin-tabular to long-prismatic. Prism faces are generally striated. Sometimes the thickness varies alternatedly in a crystal, thus causing the crystal to resemble an accordion. Crystals narrowing toward the base are not uncommon. Such crystals, if double terminated, resemble a beer-barrel. Often terminated by a simple base, but sometimes also by one or more pyramidal faces, occasionally sharpening the crystal like a pencil-point. From the Cuasso al Monte (a granophyre) in Italy paper-thin, bended, platy crystals in rose-like groups are known, that could easily be mistaken for a chlorite- or mica-mineral. Similar occurrences in Norway don`t seem to be unlikely.
diagnostical feature: the phenomenon of polycrystals of synchysite with some other cerium-fluor-carbonate can be demonstrated by means of the difference in solutibility of these minerals in nitric acid. This test is described by Donnay & Donnay (1953). Bastnäsite is insoluble in cold, concentrated nitric acid, parisite dissolves slowly, röntgenite dissolves readily, while synchysite dissolves very quickly. Even in diluted acid synchysite dissolves easily. When a polycrystal is dipped in acid for a couple of minutes, the result could be as shown at fig. 1. If performed with certain scrutiny and intelligence, this test could be used to indicate which one(s) of the 4 cerium-fluor-carbonates is(are) most likely present in a sample. Visible zoning in synchysite crystals is often the result of the presence of finely dispersed inclusions (for example hematite), and does generally not indicate the presence of a syntaxy with another cerium-fluor-carbonate mineral.
"Batterien", Nedre Eiker, Buskerud: in the miarolitic cavities of a biotite granite, the so-called Drammens Granite, white to red, prismatic synchysite crystals up to 1 mm occur. The red colour is probably due to inclusions of finely dispersed iron-oxide. Prism faces of the synchysite crystals are altered, while the base has a fresh luster. Synchysite occurs in close association with anatase, brookite and 1M muscovite. These four minerals were formed by the decomposition of REE-rich titanite under the influence of CO2-bearing solutions.
Fens-feltet, Telemark: small polycrystals of synchysite and parisite have been observed in the "rødberg", a metasomatically formed, hematite-baering carbonate rock. A resembling mineral in the "rauhuagite-rock" and in the vugs of a not nearer described rhombenprophyr-occurrence is also supposed to be synchysite/parisite in polycrystals.
Fjellsjøen, Nordmarka, Oppland: in the miaroles of a medium- to coarse-grained syenite, which can be found as erratic boulders near lake Fjellsjøen (near Gjerdingen), occur nice crystals of synchysite. The crystals are tabular to prismatic, yellow-brown to orange, generally with deep striations on the prism-planes and a lustrous base, and max. 2-3 mm large. Some crystals make the impression to have formed as a stacking of several thin-tabular crystals upon each other, resembling an accordion. Others have bellowing prism-faces, also resulting in an accordion-like form. Colour-zoning in samples sent to me by Jan Haug was common. The cause for this was not mentioned. Associates include aegirine, titanite, zircon, anatase, fluorite, calcite, pyrophanite/hematite-intergrowths, and peculiar disk-shapes crystals that may be either synchysite or bastnäsite.
Fjærland-tunnel, Sogn og Fjordane: during the construction of the Fjaerland-tunnel gneiss-klufts yielded synchysite in pale yellow to brown, (long)prismatic crystals up to .. mm. The klufts were to a certain extent calcite-filled, and had to be treated with acid in order to expose the crystals. Associates include quartz, muscovite, laumontite and others. A specimen collected by Odd Naustheller shows a group of maybe 100 to 200 intergrown synchysite crystals of a waxy yellow to brown colour. Also found were nicely developed, pale pink-brown, long-prismatic synchysite crystals of 1-2 mm., embedded in gypsum.
Gryting, Gjerstad, Telemark: in this granite pegmatite, synchysite occurs as a grey-white powderish substance in the cracks of a mineral that is probably thorogummite.
Holmøyane, Nordfjord, Sogn og Fjordane: during reconstruction of a road near/at(?) Holmøyane, synchysite in orange-brown crystals up to 5 mm was found in a gneiss-kluft. Associated are quarts, muscovite, hematite and rutile. (Odd Naustheller, pers. comm.)
Kristians søndre stoll, Kongsberg, Buskerud: in 1961 Sæabö & Neumann discovered synchysite on a museum specimen from 1865, as 0,2 mm long, pale yellow, hexagonal crystals, associated with anatas, albite, quarz, chlorite and pyrite. It is likely that there is no relationship between this paragenesis and the silver-veins.
Midtmoen, Øståsen, Oppland: the occurrence of synchysite at a roadcut has been described by L. Kvamsdal in Stein 1/1993. However, the improvement of fylkesveg 23 resulted in dozens of smaller, hitherto nearly unexamined roadcuts. In one of these synchysite was found in a single specimen as gemmy, lustrous hexagonal crystals of a fine yellow to yellow-orange colour. Remarkable is the presence of two different crystal-habits on the same specimen: some crystals show a combination of prism, base and very sub-ordinate pyramidal faces, while others are terminated by a multitude of pyramidal faces, forming pencil-pointed crystals. This roadcut has been examined only superficially. At Midtmoen as such, synchysite occurs as yellow to brown, prismatic, hexagonal crystals with lustrous base up to 3 mm. Many of the crystals seem to be affected by surface weathering, and have a dull white-yellow colour. The entire area has good potential for finding more synchysite, and many of the minerals as described in Kvamsdal`s article. We await with great anticipation the construction of the new road between Hadeland and Gardermoen airport, which will cut through this syenite pluton somewhat more to the south.
Nittedal, Åkershus: Eldjarn & Fylling (1982) mention the find of synchysite in a not nearer described nordmarkite occurrence near Nittedal, as tabular crystals.
Sande i Gaular, Sogn og Fjordane: this occurrence has been described by Helge Samuelsen in Stein 1/1993. The here occurring synchysite is probably the best found in Norway so far. The synchysite occurs in Alpine type of veins in gneiss, as yellow, orange-brown to even reddish, longprismatic crystals up to 6 mm. The prisms are typically striated and dull, while the base has a fresh luster. Many of the crystals narrow towards the base. The associated minerals are: quarz, calcite, hematite, albite, barite and xenotime.
Sandungen i Asker, Åkershus: polycrystals of synchysite /parisite occur in cavities of a rhombenprofyr (RP2b).
Solumsåsen pukkverk, Holmestrand, Vestfold: in the cavities of a rhombenporfyr (RP1) occur pale yellow to orange brown, tabular to prismatic polycrystals of parisite/synchysite, with a maximum size of 2-3 mm. In general, parisite seems to dominate over synchysite. But tests indicate that also pure synchysite crystals, or polycrystals with dominance of synchysite over parisite, occur. It seems therefore, that indiscriminate labelling of specimens from this occurrence as "parisite" is incorrect. Associated species include albite, calcite, anatase and bertrandite.
Vassbråa, Øståsen, Oppland : in the miaroles of a medium- to coarse-grained syenite a synchysite-resembling mineral occurs, as tabular to short-prismatic hexagonal crystals of orange-brown colour. Associates include titanite, zircon, pyrophanite(?), stilbite, heulandite and others. This occurrence is essentially un-examined, but seems to have potential for yielding very esthetic specimens.
The above described occurrences of synchysite are all of relatively recent discovery. The likelyhood that intensified examination of the vast metamorphic areas in south, west, middle and north Norway will result in new finds of synchysite is large. Some of the syenites north of Oslo have a nearly unlimited potential for yielding specimens of synchysite. Some rhombenporphyric lava-flows in the Oslo-area contain large quantities of excellent synchysite/parisite polycrystals. Already now, it is reasonable to say that synchysite and/or polycrystals of synchysite with particularly parisite occur in Norway in excellent specimens, matching those from internationally better known occurrences.
This article is dedicated to Helge Samuelsen, who, for God knows what reason, died in a car-accident early this year. I am much indebted to him for spontaneously sending me a number of excellent synchysite- specimens from the Sande quarry, after telling him about my intention to write about synchysite from norwegian occurrences. Stein wishes to thank Odd Naustheller for information about synchysite from the Fjaerland-tunnel and from Holmøyane, and sending specimens for having photographed. I would like to thank Jan Haug for sending me synchysitt-samples from Fjellsjøen. I am greatly indebted to Alf Olav Larsen for important and exciting information about the syntaxy between synchysite and the other cerium-fluor-carbonates.
-Donnay, G. & Donnay, J:D:H: (1953): The crystallography of bastnaesite, parisite, roentgenite and synchysite. American Mineralogist, 38, 932-963.
-Eldjarn, K. & Fylling, H. (1982): Drusemineraler fra granitter og syenitter i Oslo-feltet. Nags-nytt, okt./des. 1982, 6-23.
-Fleischer, M. & Mandarino, J.A. (1991): Glossary of mineral species 1991. The Mineralogical Record Inc.
-Neumann, H.(1983) : Norges mineraler. Norges Geologiske undersøkelse, skrifter 68, p. 100
-Kvamsdal, L. (1993): noen mineraler fra nordmarkitten mellom Roa og Maura. Stein, jan/mars 1993, 30-45
-Nesby, W.H.(1989): Mineraler fra Fjaerlandstunnelen. Nags-nytt, jan./mars 1989, p. 52.
-Petersen, O.V. & Secher, K. (1984): Der Narssârssuk-Pegmatit; Magma, November/Dezember 6/84, 44-57.
-Raade, G (1969): Cavity minerals from the Permian Biotite Granite at Nedre Eiker Church. Norsk Geologisk Tidskrift 49, 227-239.
-Ramdohr, P. & Strunz, H. (1976): Klockmann`s Lehrbuch der Mineralogie. Ferdinand Enke Verlag, Stuttgart.
-Samuelsen, H. (1993): Sogn 1992. Stein, jan/mars 1993, 2 + 64-67.