GEOLOGIJA 40, 283-289 (1997), Ljubljana 1998
Zn-rich pyroxenes from the ore occurrences in the mixed series
in the upper part of the Babuna River, Macedonia
Simeon Jancev
Faculty of Technology and Metallurgy, Sv. Kiril i Metodij University
91000 Skopje, Macedonia
Key words: new mineral varieties, very rare minerals, peculiar Zn-rich aegirine-
augite, electron micro-probe, Macedonia
Abstract
The basic purpose of this report was the determination of very fine-grained (cca
0.02-0.05 mm) corroded Zn-rich pyroxenes relics that occur in the mineralized dolo-
mite marbles and baryte schists.
The determination was performed particularly by means of the electron micro-
probe analysis that established the new mineral varieties of Zn-rich aegirine-augite
composition. The examined pyroxenes were confirmed as pyroxenes, and establi-
shed by X-ray powder data inside of a complex polyphase mineral system consi-
sting of Zn-rich pyroxenes, Zn-rich richterite, Zn-rich phologopite and baryte.
Introduction
According to earlier examinations, quartz-cymrite, baryte-cymrite, hyalopha-
ne-cymrite, baryte - Zn-rich richterite - Zn-rich glaucophane - tilasite schists we-
re discovered in the surrounding area of the high alkaline aegirine meta-rhyolite
in the frame of the so called mixed series of the upper part of the Babuna River re-
gion (Jancev, 1975). In this region were discovered next to common (baiyte, galena,
cleiophane, hematite, pyrite etc.) also very rare minerals (gahnite, piemontite, fran-
klinite by Baric (1960) and Baric and Ivanov (1960). By Jancev (1975,
1984a, b, 1990, 1994) and Jancev and Bermanee (1997) were discovered later
cymrite, sanbomite, hedyphane, celsiane, Pb-piemontite, hancockite, Mn-rich hancoc-
kite or Pb-rich piemontite, hyalophane, tilasite, Sb-rich gahnite, Sb-rich franklinite,
Zn-rich richterite, and Zn-rich glaucophane.
Experimental
The Zn-rich pyroxenes samples were primarily reported macroscopic as discrete
discontinuous layers or lenses (the thickness of which was around or less than 1 mm)
enclosed in dolomite marbles mineralized with baryte, tilasite, Pb-piemontite etc.
284_Simeon Jančev
Later, Zn-rich pyroxenes were discovered in baryte-Zn-rich richterite-Zn-rich glau-
cophane-tilasite schists collected many years ago from difíerent parts and levels of
the complex polymetallic ore occurrences. These Zn-rich pyroxene lenses are dark
greenish-yellowish coloured and resembling epidote. Besides Zn-rich pyroxene layers
or lenses in the aforementioned dolomite marbles and baryte schists, also impregna-
tions and disseminated mineralizations of these minerals were discovered.
Zn-rich pyroxenes samples were examined by microscopic methods in thin secti-
ons. These examinations show that Zn-rich pyroxenes associations in the frame of the
aforementioned lenses or disseminated mineralizations are very fine-grained (less
than 0,05 mm) corroded relics and replacements by the younger hydrothermal mine-
rals representing a real handicap for optical and powder X-ray diffraction examinati-
ons (Fig. 2 to Fig. 6). Therefore, the considered Zn-rich pyroxenes were determined by
means of the electron micro-probe analysis (performed by S. Korikowski from IGEM -
AN in Moscow, Russia, and by H. Stančev from IGG in Sofia, Bulgaria) that furnished
the preliminary results which were very important for further examinations.
The chemical composition of the minerals was determined at more points scanning
at different randomly selected positions from center to the edge of the grain. Chemi-
cal formulas were obtained by standard procedures.
The examined pyroxenes were confirmed also by X-ray powder data in a complex
poly-phase mineral system containing pyroxenes, richterite, phlogopite in the frame
of the treated fine-grained lenses of the mineralized dolomite marbles.
Acknowledgement. I am deeply thankful to my colleagues H. Stančev and S. Kori-
kowski for electron micro-probe analysis of the described minerals from Macedonia.
Results and discussion
In this report are presented data of the Zn-rich pyroxenes that are peculiar mine-
ral varieties of the Zn-rich aegirine-augite composition.
Zn-rich aegirine-augite
Occurrence. In the frame of discrete greenish-yellowish lenses or layers up to 1
mm in thickness, enclosed in dolomite cipolins, Zn-rich aegirine-augite relics were
discovered in form of very fine-grained (0,01-0,05 mm), irregular, fibrous, rounded
and corroded grains. Besides of Zn-rich pyroxenes in these cipolins were determined
Sb-rich gahnite, Sb-rich franklinite, Zn-rich richterite, Zn-rich phlogopite as well as
typical hydrothermal minerals - quartz, albite, dolomite, baryte, tilasite etc.
X-ray powder data. The greenish-yellowish lenses were separated of the rock by
means of a binocular microscope and then treated by classical X-ray diffractometer
procedure (Cu К^ / Ni, 40 kV, 20 mA). In the examined sample (Fig. 1) were deter-
mined pyroxenes (d(Â)6,30, 4,38, 3,650, 3,350, 3,161, 2,961 etc.), richterite
(d(Â)8,19, 3,350, 3,220, 3,160, 2,961 etc.), phlogopite (d(Â)10,04, 3,350, 3,220, 3,022,
2,613 etc.).
Chemistry. In the aforementioned corroded pyroxen relics by means of ten elec-
tron micro-probe analyses performed by H. Stančev (samples 1, 2, 4,...10) and S. Ko-
rikowski (sample 3) the Zn-rich aegirine-augite varieties were determined as fol-
lows (Tab. 1):
Zn-rich pyroxenes from the ore occurrences in the mixed series_3
~ Table 1. Chemical composition of Zn-rich aegirine-augite samples (%)
The examined Zn-rich aegirine-augite samples show an evident and very strong li-
near correlation between MgO and ZnO contents. So, in the aegirine-augite samples
containing more than 10% MgO a maximum of 4-8 % ZnO was reported, while sam-
ples with less MgO contents (0,35-5,5 % MgO) show 0,44-0,85 % ZnO.
Examined samples No. 3, No. 5 to No. 8 and No. 10 (with cca 4-8 % ZnO respecti-
vely) could be considered as peculiar and probably new mineral varieties - Zn-rich
aegirine-augite inside of the aegirine-augite series vis á vis the Zn-rich schefferite
(with 3,31-3,38 % ZnO) and jeffersonite (with 7,14-10,15 % ZnO), (P a 1 a c h e, 1960).
Genesis
The aforementioned Zn-rich pyroxenes determined as Zn-rich aegirine-augite we-
re discovered in mineralized dolomite marbles in forms of fine-grained (cca 0,01-0,05
mm) relics very intensively replaced by younger hydrothermal minerals (baryte, quartz,
tilasite etc.) and consequently considered as a contact-metasomatic product that ori-
ginated at highest temperatures immediately after spinels of gahnite-franklinite type
from the post-magmatic oversaturated fluids.
286_Simeon Jančev
Conclusions
In dolomite marbles and baryte Zn-rich richterite-tilasite schists from a mixed se-
ries in the Precambrian complex of the Pelagonian massif in the upper part of the
Babuna river, Macedonia, were discovered the Zn-rich pyroxenes as follows:
-	Zn-rich aegirine-augite containing cca 0,5-0,8% ZnO, and
-	Zn-rich aegirine-augite with cca 4-8% ZnO as a peculiar mineral variety inside
the aegirine-augite series.
The aforementioned Zn-rich pyroxenes are considered as typical contact-metaso-
matic products originated by the action of oversaturated post-magmatic fluids in do-
lomite marbles and baryte-Zn-rich richterite-tilasite schists.
References
Baric, L j. 1960: Piemontit, Gahnit und Rutil aus dem Fundort der Blei und Zinkerze bei
dem Dorfe Nežilovo in Mazedonien. - Glasnik prirod, muzeja, ser. A., 13, Beograd.
Baric, Lj. & Ivanov, T. 1960: Mineral Vergesellschaftung in der Umgebung des Dorfes
Nežilovo am Jakupica-Gebirge in Mazedonien. - Bull, sei., 5, 2, Zagreb.
Jančev, S. 1975: Ore occurrence of cymrite at the village of Nežilovo in Macedonia. -Bui.
sci.. A, 20, 9-10. Zagreb.
Jančev, S. 1984a: Pojave arsenala tipa tilazita (tilasite) i hedifana (hedyphane) iz rudnih
pojava barita iz mešane serije izvorišnog dela r. Babune, Makedonija. - JAM, Beograd.
Jančev, S. 1984b: A mineral of hedyphane (Pb,Ca)5(As04)3 Cl structure from the mixed
series of the Babuna river, Macedonia. - Geologica Macedonica, Štip.
Jančev, S. 1990: Pb-piemontit od rudnite pojavi vo mešanata serija na izvorišniot del od
r. Babuna, Makedonija. - XII Kongres geologa Jugoslavije, II, 62-66, Ohrid.
Jančev, S. 1994: Ba-rich and Zn-rich silicate minerals, Sb-rich gahnite and braunite from
the ore occurrences in the mixed series of the Pelagonian massif at the village of Nežilovo, Ma-
cedonia. - Geologica Macedonica, 8, 1, 39-44, Štip.
Jančev, S. & Bermanee, V. 1997: Solid solution between epidote and hancockite
from Nežilovo, Macedonia. - Geologica Croatica, Zagreb (in press).
Palache, Ch. 1960: The minerals of Franklin and Sterling Hill, Sussex County, New Jer-
sey. - Geological Survey Professional Paper 180, U.S. Government Printing Office, Washington.
Zn-rich pyroxenes from the ore occurrences in the mixed series
287
Fig. 1. X-ray powder diagram of Zn-rich aegirine-augite (py) associated with Zn-rich richterite
(r), Zn-rich phlogopite (p.), baryte (by), chlorite (ch) in the frame of a veinlet enclosed in the
mineralized dolomite marbles
Fig. 2. Corroded and replaced Zn-rich aegirine-augite (a) relics by baryte (b) in
baryte schists (N-;-, photo: S. Jancev)
288
Simeon Jančev
Fig. 3. An association of Zn-rich aegirine-augite (a), tilasite (t), ore minerals (o)
inside of a tilasite veinlet enclosed in baryte (b) schist (N+, photo: S. Jančev)
Fig. 4. An association of Zn-rich aegirine-augite (a) and Zn-rich richterite (r)
enclosed in baryte (b) schist (N+, photo: S. Jančev)
Zn-rich pyroxenes from the ore occurrences in the mixed series
289
Fig. 5. Replacements of Zn-rich aegirine-augite (a) by Zn-rich richterite (r) inside
of baryte (b) schist (N+, photo: S. Jančev)
Fig. 6. Super fine-grained associations of Zn-rich aegirine-augite (a) replaced by
Zn-rich richterite (r) fibres enclosed in dolomite marble (N+, photo: S. Jancev)