GEOLOGICA CARPATHICA, 48, 2, BRATISLAVA, APRIL 1997
137–140
SPINEL-HORNBLENDE-ANTHOPHYLLITE (NEPHRITOID)
NEOLITHIC AXES FROM WESTERN SLOVAKIA
DUŠAN HOVORKA
1
, UDMILA ILLÁŠOVÁ
2
and SERGEY KORIKOVSKY
3
1
Department of Mineralogy and Petrology, Faculty of Sciences, Comenius University, Mlynská dolina, 842 15 Bratislava, Slovak Republic
2
Archaeological Institute, Slovak Academy of Sciences, Akademická 2, 949 21 Nitra, Slovak Republic
3
Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry, Russian Academy of Sciences, Staromonetny per. 35,
109017 Moscow, Russia
(Manuscript received June 20, 1996; accepted in revised form October 9, 1996)
Abstract:
Among artifacts from several localities/sites in western Slovakia (the Malé Karpaty Mts. and the Danube
Upland (Podunajská pahorkatina)) those composed of green Al-rich spinel, hornblende and anthophyllite are charac-
teristic. Other minerals (olivine, clinozoisite, muscovite, ilmenite, magnetite and sphene) are present in accessory
amounts. The stones bear several characteristics of nephrites. In paper we use the common term nephritoids for various
varieties of the discussed rocks. Primary occurrences of these Al-rich spinel-hornblende-anthophyllite rocks are yet
known. On the basis of the predominance of hornblende and anthophyllite, the rocks under consideration are thought
to be products of medium-temperature metamorphism of spinel bearing orthopyroxene-clinopyroxene rocks
(ferroultramafics) under static conditions and high P/H
2
O.
Key words:
Neolithic, axes, (Al-rich) spinel-hornblende-anthophyllite (nephritoid) rocks.
Introduction
During the last decade a wealth of new information on for-
merly uncommon rock-type occurrences within the Western
Carpathian territory have been published, but rock of Al-
spinel-hornblende-anthophyllite composition are still un-
known. Occurrences of tools made from this rock type are
shown in the Fig. 1. In an attempt to find the original rock-
bodies we have looked at the published information on adja-
cent geological units as well.
Although Central Europe, (the Bohemian Massif, Eastern
Alps and Western Carpathians), has several geological units
containing greenschists (actinolite, tremolite, hornblende and
chlorite schists); the presence of chlorite sheets, together with
pronounced preferred orientation (= foliation), limits the use of
such rock-types as a raw material for polished tools. On the
other hand rocks with radial orientation of amphibole needles
or felt-like fabric of given rocks have appropriate technical fea-
tures to be used as raw material for polished industries.
On the basis of generally accepted principles of metamor-
phic petrology, regional metamorphic recrystallization of ul-
tramafics could be favorable for the origin of radial or felt-
like fabrics of rocks commonly used as raw materials for
Neolithic polished industries.
Petrology of rocks
The spinel-hornblende-anthophyllite, anthophyllite-horn-
blende and hornblende schists (felses), used as the raw ma-
terial of Neolithic axes/adzes from several localities in
western Slovakia, have some common features which could
be summed up as follows:
i) all discussed petrographic varieties are, observing them
by naked eyes, aphanitic to very fine-grained tough rocks of
generally dark (dark grey, dark greyish-green, dark green)
colour,
ii) they are mostly massive (Fig. 2), or in some thin sec-
tions slightly foliated (Fig. 3),
iii) they lack sheet silicates (accessory amounts of chlorites are
exceptions). This is one of the supposed aspects of the good
quality of this raw material for production of polished industries,
vi) the very fine-grained character of the rock studied (less
than 0.l mm) does not allow the determination of their quanti-
tative mineral composition. On the basis of estimation in sev-
eral thin sections, the volume of hornblende and anthophyl-
lite varies in the range 60–95 per cent. Total absence of
quartz, and feldspars is characteristic.
vii) The presence of colourless magnesian hornblende, to-
gether with other Al-containing phases (green Al-spinel, cli-
nozoisite) allow us to suppose that Al-silicates were constit-
uents of the protolith. The high XFe in the minerals present
is a genetically important value. It is not typical for ordinary
ultramafics and favours a ferroultramafic protolith for the
rocks studied. The mineral association of the rocks under
discussion indicates P-T conditions of metamorphic recrys-
tallization (there is no doubt that the rocks under consider-
ation are metamorphites) corresponding to those of the low
temperature area of the amphibolite facies. A contact-ther-
mic origin may be assumed comparable with those of the
central parts of contact aureoles of granitic massifs.
viii) The dominant phases are hornblende and anthophyl-
lite indicating recrystallization under high P/H
2
O conditions.
Mineral association
The leading minerals of the rock types studied are horn-
blende and anthophyllite. They form longcolumnar till fi-
brous, often felty matrix, in which grass-green spinels are ir-
138 HOVORKA, ILLÁŠOVÁ and KORIKOVSKY
regularly distributed (up to 20 per cent). In accessory
amount crystals of clinozoisites, olivines, ilmenites, magne-
tites, sphenes and muscovites are present. Hornblende is
colorless and, based on analytical results (Tab. l), it is repre-
sented (XFe 0.24–0.27) by low Na-calcic hornblende of the
edenite-hornblende series (Leake l978).
The anthophyllite has low contents of Al
2
O
3
(l.3–l.6 per
cent) and an appropriate amount of iron (XFe 0.30–0.3l).
Al-spinels (Tab. 2) contain solution of Cr
2
O
3
(0.l–l.8 wt.
per cent) and they have medium Fe content (XFe 0.54–0.6l).
The above mentioned 3 phases represent 93–96 per cent of
the bulk composition of the rocks under consideration.
Rare Fe-rich olivine crystals (XFe 0.4l) are in full equilib-
rium with amphiboles and spinels and are of metamorphic
origin. Clinozoisites are characterized by a low content of
Fe
2
O
3
(0.5–4.3 per cent). The very rare flakes of muscovite
(Tab. l) are characteristic by a low natrium content. The
very fine-grained sphenes are practically without Al. Ore
minerals are represented by homogeneous magnetite and il-
menite crystals in intergrowth with rutile and sphene. So
their origin by breakdown of titanomagnetite is probable.
Pre-metamorphic protolith
The feldspars- and quartz-free association and stability of the
spinel-hornblende-anthophyllite assemblage allow us to sup-
pose that the protolith (orthopyroxene-clinopyroxene-spinel
rocks) recrystallized under epidote-amphibolite to lowgrade
amphibolite facies conditions. The spinel-rutile-sphene inter-
growths, products of breakdown of original titanomagnetite,
are evidence in favour of this.
However the determined mineral composition of the rock
studied is not in agreement with the supposed ultrabasic pro-
tolith. The main objectives are as follows:
a — the present minerals are characterized by elevated XFe
in comparison to minerals of common ultramafite rocks,
b — two of the three rock-forming minerals: hornblende and
spinel, have a high Al content. Two of the accessories present
(muscovite and clinozoisite) are also Al-rich. On the basis of
the facts the protolith should have contain a substantial
amount of alumina, significantly higher than the Al-content
in ultramafites.
In conclusion we suppose that the spinel-hornblende-an-
thophyllite rocks originated by metamorphic recrystallization
of ultramafic two-pyroxene cumulate of the gabbro-noritic
clan. Only a such type of the protolith could explain the ele-
vated content of Al and Fe simultaneously and the lower con-
tent of Cr
2
O
3
in metamorphic (and in such way also in origi-
nal magmatic) spinels.
The phase equilibria of the spinel-hornblende-anthophyllite
rocks are presented in diagrams of Ca-Al-Mg, Fe and Fe-Si-Al
(Fig. 4). They do not exclude the possibility that the metamor-
phic association originated by metamorphic recrystallization of
two-pyroxene-spinel cumulate. The identified variety of meta-
morphic olivine indicates that in the pre-metamorphic protolith
this mineral was also rare, so the original rock was relatively
SiO
2
saturated.
In connection with the problem of the raw material prove-
nance it ought to be taken into consideration that even spinel-
hornblende-anthophyllite axes/adzes have been found on several
western Slovak sites, no rock debris deposits were reported dur-
ing archaeological surveys of these sites. So it should be expect-
ed that finished tools have been transported. Taking into account
the identical mineral composition of the finds studied, we sup-
pose that one rock-body or rock-bodies of identical origin are the
source of raw material for spinel-anthophyllite axes/adzes.
Fig. 1.
Localities with spinel-hornblende-anthophyllite axes: 1 —
Bratislava-Dúbravka, 2 — Blatné, 3 — Ružindol, 4 — Žlkovce, 5
— Lefantovce, 6 — Nitriansky Hrádok, 7 — Bajč, 8 — Santovka,
B
— Bratislava.
Fig. 2.
Random orientation of anthophyllite + hornblende longco-
lumnar crystals of variable size. Ružindol, magn. 30
×
, X polars.
Fig. 3.
Slightly expressed preferred orientation of longcolumnar an-
thophyllite + hornblende. Nitriansky Hrádok, magn. 30
×
, X polars.
SPINEL-HORNBLENDE-ANTHOPHYLLITE NEOLITHIC AXES 139
Supposed provenience of the raw material
In the Western Carpathians no comparable rocks have been
described up to now. An up to date survey of the main rock
types used as raw material for Neolithic-Eneolithic axes/adzes
is given in a paper by Illášová & Hovorka(1995). The only oc-
currence of anthophyllite bearing rock, forming the reaction
rim around the ultramafic body in the Veporic Unit (central
Slovakia: Hovorka l967) due to its extremely small extent can-
not be counted among the possible sources of raw material of
the discussed axes.
The Bohemian Massif is the adjacent geological unit situat-
ed west of the described localities. The Moldanubian Varied
Fig. 4.
Associations of rocks studied on Ca-Al-Mg,Fe, and Si-Al-
Mg,Fe diagrams.
Table 2:
Microprobe analyses of spinels (Spl), clinozoisites (Czo), ilmenites (Ilm), magnetites (Mag) and titanite (Ttn).
Table 1:
Microprobe analyses of hornblendes (Hbl), anthophyllites (Ath), olivine (Ol) and secondary muscovites (Ms).
H b l
A th
O 1
M s
Sam p le
L -5
D -P A -1
R -r
L -5
D -P A -1
R -r
R -r
D -PA -1
R -r
1
2
3
4
5
6
7
8
9
1 0
SiO
2
4 9 .8 1
4 7 .6 8
4 8 .4 1
4 9 .6 6
5 5 .2 1
5 5 .1 8
5 5 .2 0
3 5 .2 1
4 5 .6 2
4 5 .4 2
T iO
2
0 .5 1
0 .6 2
0 .5 9
0 .6 7
0 .1 5
0 .1 4
0 .0 1
-
-
0 .0 8
A l
2
O
3
9 .2 3
1 1 .2 3
1 0 .2 2
9 .7 2
1 .3 7
1 .5 8
1 .6 2
0 .1 1
3 7 .9 9
3 8 .6 5
FeO
9 .5 4
9 .2 4
1 0 .1 0
9 .5 9
1 7 .3 4
1 6 .9 8
1 7 .0 2
3 5 .0 8
0 .4 8
0 .5 4
M n O
-
0 .0 1
0 .0 5
0 .0 7
0 .3 7
0 .1 7
0 .4 0
0 .3 4
-
0 .0 6
M g O
1 6 .6 3
1 6 .0 7
1 5 .6 7
1 6 .0 8
2 2 .0 2
2 2 .3 7
2 2 .0 4
2 7 .8 7
0 .0 1
0 .2 9
C aO
1 1 .4 3
1 1 .6 3
1 1 .5 1
1 1 .3 9
1 .0 2
1 .2 1
1 .7 6
0 .0 1
-
0 .5 8
N a
2
O
0 .7 2
1 .1 5
1 .2 3
0 .4 7
0 .0 5
0 .1 1
-
-
0 .3 5
0 .5 9
K
2
O
0 .2 5
0 .2 2
0 .1 7
0 .0 5
0 .0 4
-
0 .0 4
-
1 0 .9 3
9 .8 4
T o tal
9 8 .1 2
9 7 .8 5
9 7 .9 5
9 7 .7 0
9 7 .5 7
9 7 .7 4
9 8 .0 9
9 8 .6 1
9 5 .3 8
9 6 .0 5
Si
7 .0 2
6 .7 9
6 .8 8
7 .0 1
7 .8 2
7 .7 9
7 .8 0
0 .9 9
3 .0 1
2 .9 6
A l
IV
0 .9 8
1 .2 1
1 .1 2
0 .9 9
0 .1 8
0 .2 1
0 .2 0
-
0 .9 9
1 .0 4
A l
V I
0 .5 5
0 .6 7
0 .5 9
0 .6 3
0 .0 5
0 .0 5
0 .0 7
-
1 9 8
1 .9 3
T i
0 .0 5
0 .0 7
0 .0 6
0 .0 7
0 .0 2
0 .0 2
-
-
-
-
Fe
1 .1 2
1 .1 0
1 .2 0
1 .1 3
2 .0 5
2 .0 0
2 .0 1
0 .8 3
0 .0 2
0 .0 3
M n
-
-
0 .0 1
0 .0 1
0 .0 4
0 .0 2
0 .0 5
0 .0 1
-
-
M g
3 .5 0
3 .4 1
3 .3 2
3 .3 8
4 .6 6
4 .7 1
4 .6 4
1 .1 7
-
0 .0 3
C a
1 .7 3
1 .7 7
1 .7 5
1 .7 2
0 .1 5
0 .1 8
0 .2 7
-
-
0 .0 4
N a
0 .2 0
0 .3 2
0 .3 4
0 .1 3
0 .0 2
0 .0 3
-
-
0 .0 4
0 .0 5
K
0 .0 4
0 .0 4
0 .0 3
0 .0 1
0 .0 1
-
0 .0 1
-
0 .9 3
0 .8 2
X
F e
0 .2 4
0 .2 4
0 .2 7
0 .2 5
0 .3 1
0 .3 0
0 .3 0
0 .4 1
Spl
C zo
Ilm
M ag
Ttn
Sam ple
L5
D -PA -1
R -r
L-5
D -PA -1
R -r
D -PA -1
1
R -r
2
R -r
1
R -r
2
1
2
3
4
5
6
7
8
9
10
11
12
SiO
2
0.01
0.08
0.07
0.10
39 .3 6
38 .9 3
38 .7 3
0.11
0.09
0.09
0.55
30 .4 0
TiO
2
-
0.17
0.07
0.09
-
0.03
0.10
50 .9 2
51 .0 3
50 .5 5
0.01
39 .7 1
A l
2
O
3
59 .7 4
62.8 7
61 .5 8
60 .6 9
33 .5 1
31 .4 9
32.3 0
-
0.19
0.09
-
0.39
FeO
6.69
24 .4 4
26 .9 3
27 .9 5
0.53 *
4.30 *
3.49 *
47 .6 5
46 .8 3
47 .8 8
99 .0 5**
0.39
M nO
0.04
0.01
0.14
0.13
0.12
0.08
0.07
0.37
0.95
0.70
0.01
-
M gO
10 .4 7
11 .5 8
10 .21
9.84
-
0.28
0.34
0.54
0.17
0.12
0.06
0.11
C aO
-
0.07
0.03
-
24 .1 2
22.6 2
22.8 2
0.04
0.08
0.19
0.21
28.16
C r
2
O
3
1.81
0.25
0.23
0.10
-
-
-
0.05
-
-
0.01
0.03
Zn O
0.66
0.17
0.59
0.82
-
-
-
-
-
-
-
0.37
To tal
9.41
99 .5 4
99 .8 5
99 .7 2
97 .6 4
97 .7 3
97 .8 6
99 .6 8
99 .3 4
99 .6 2
99.90
99.56
X
Fe
0.59
0.54
0.60
0.61
*
— all Fe as Fe
2
O
3
;
**
— all Fe as FeO;
1
— from separate grains;
2
— from the ilmenite-titanite-rutile intergrowths
140 HOVORKA, ILLÁŠOVÁ and KORIKOVSKY
Group in particular bears occurrences of anthophyllite gneiss-
es. Migmatized types of anthophyllite gneisses and biotite-
cordierite-anthophyllite gneisses have been reported from the
vicinity of Žárovná in southern Bohemia (Vrána l963). Antho-
phyllite gneisses (composition: anthophyllite — 54–56 %, bi-
otite — 24–28 %, plagioclase, quartz, actinolite and accesso-
ries) have been described from the gallery south of Český
Šternberk by Zikmund (l97l). Amphibolites with anthophyllite
have also been reported from this geological unit in the past
(Ginějko-Savicka l928; Orlov l93l).
Another genetic group of anthophyllite monomineral and
anthophyllite bearing rocks is that of reaction rims round ba-
sic and especially ultrabasic rock-bodies located within
gneisses and migmatites of the above mentioned geological
unit (Kudělásková et al. l96l).
Comparing the spinel-hornblende-anthophyllite rock stud-
ied with those described from the Moldanubian Varied Group
(citation see above) and with those from northern Bohemia de-
scribed by Granzer (l933), Hejtman (l962) and especially by
Bukovanská (l992) there exist substantial differences:
a — although from the northern Bohemian metamorphics
several types have been described (tremolite, actinolite, horn-
blende bearing rocks) no rhombic amphiboles have been re-
ported in the past,
b — among minerals of rock under consideration no author
described the presence of green, Al-rich spinel. It should be
pointed out that in some of the thin sections green spinel is one
of the substantially present mineral phases.
The distribution of polished Neolithic/Eneolithic artifacts is
more-or-less regular in the whole territory of western Slovakia.
Among the most hopeful areas, that of northern Bohemia
seems to be an area of primary occurrences of stony raw mate-
rial for the Neolithic/Eneolithic polished goods. From that area
Bukovanská (l992) described actinolite and actinolite-horn-
blende schists with characteristic radial structures of amphib-
oles and general massive to foliated cleavage. In northern Bo-
hemia Precambrian-Early Paleozoic basic to ultrabasic
volcanics and especially volcaniclastics have been thermally
recrystallized within the contact aureole of the Variscan
Krkonoše-Jizerské hory Mts. granitic massif. Thus contact-
thermic recrystallization under static conditions and high
PH
2
O, represents a second metamorphic episode (following
the greenschist facies metamorphism of regional extent).
Discussion
From the genetic point of view the association Al-spinel +
hornblende + anthophyllite is the most important. For the so-
lution of the protolith problem we use the following thin sec-
tion observations:
— we studied the above mentioned mineral association in
several thin sections, but we found relics of rhombic pyrox-
ene of estimated hypersthene chemistry in only one,
— mentioned relic is surrounded by a felty matrix com-
posed of hornblende + anthophyllite and green Al-rich spinel,
— the irregular distribution of green spinels, but simulta-
neously its observed occurrences in spatially limited
“fields” indicates their origin from the breakdown of origi-
nal orthopyroxene following the equation:
orthopyroxene + H
2
O = anthophyllite + Al-rich spinel.
The shape (longcolumnar to needle-like) of the prevailing
anthophyllite, structure (felty, often radial), submicroscopic
dimensions of phases allow us to use denomination “nephri-
toids” for the whole group of, by naked-eyes aphanitic, dark,
massive to slightly schistose rock types free of quartz, feld-
spars and chlorite.
Conclusions
In this paper we offer information on an unusual rock-type
which was used in Neolithic time period as a relatively frequent
type of raw material. No bodies of Al-rich spinel-hornblende-an-
thophyllite rocks are known outcropping in Central Europe. The
relatively uniform character of the studied artifacts suggests that
one rock-body, or several rock-bodies of identical origin ought to
be considered as the source of raw material for these artifacts.
Distribution of spinel-anthophyllite Neolithic/Eneolithic
axes within western Slovakia, and lack (any such artifacts have
been found yet) of artifacts made from discussed rock type
within the central as well as in the eastern Slovakia, indicate
that the primary occurrence/occurrences were located west of
the archaeological sites with axes/adzes made of spinel-antho-
phyllite rocks.
The submicroscopic grain-size, mineral composition as well
as felty, mostly massive and often radial fabrics allow us to de-
nominate the rocks under discussion as “nephritoids”.
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