Nakamura, Takeshi

Osaka City University Repository

• 
Journal of Geosciences， Osaka Clty UniVerslty 
Vol. 8， Art. 1 
Fe bruary， 1964 
Some Characteristic Features of Ferberite 
from the Ashio Copper Mine， J'apan 
(Studies on Minera]s from 
the Ashio Copper Mine，' Japan 11)* 
Takeshi NAKAMURA 
1. Introduction 
Wolframite occurs as thin tabular， thin platy or slender needle crystals from 
the Ashio copper mine (KISHI， 1933; ITO and SAKURAI， 1947 ; NAKAMURA， 1951， 1954). 
During the course of a study of the mineral deposits of the Ashio copper 
mine， the subvolcanic hydrothermal deposits with copper， zinc， lead， bismuth and 
tin ores， the author was able to examine the mode of occurrence and mineralo-
gical features of this mineral. The chemical properties and X-ray studies clari-
fied this mineral to be the ferberite with a composition near the Fe-end member 
of the wolframite mineral series. 
In this paper， the mode of occurrence and mineralogical features of ferberite 
from the mine will be described and further some characteristic features of the 
wolframite mineral series from the subvolcanic hydrothermal deposits in Japan 
will be shown from the vi¥ew point of ore genesis. 
The author wishes to express his sincere thanks to Professor Takeo W ATANA-
BE of University of Tokyo for giving generous support and advice on this work. 
Sincere thanks of the author are also due to Professor Goro ASANO of Kyushu 
University， to Professor Nobuo KATAYAMA of University of Tokyo and to Professor 
Kiyoshi T AKIMOTO of Kyoto University， for their kind instruction to this study. 
He is also very much indebted to the geological engineers of the Furukawa 
Mining Co. Ltd.， and of the Ashio Mining Office， and to members of Department 
of Geosciences， Osaka City University. Final1y， he wishes to thank the grants 
from the Scientific Research Fund of the Ministry of Education which enabled 
him to carry on a part of his field and laboratory works. 
2. Mineralogical properties of wolframite mineral series 
The wolframite mineral series is a complete isomorphous series between Mn 
W04 and FeW04・ Speciesnames applied to particular ranges of composition 
are shown in Table 1. The Fe-rich members (80 to 1009o Fe) are commonly 
referred to as ferberites， Mn-rich members (80 to 10096 Mn) as huebnerites， and 
al1 others as wolframi tes. 
* Contribution from the Department of Geosciences， No. 146. 
1 
， 
2 Takeshi NAKAMURA 
Table 1. Wolframite mineral series. 
Atomic per cent Corresponding 
Species name substitution weight percentages 
Mn Fe MnO FeO 
Huebnerite 100 -80 % o -20 % 23.4 -18.7% 0-4.85ぢ
Wolframite 80 -20 % 20 -80労 18.7-4.7% 4.8 -18.9% 
Ferberite 20 - 。% 80 -100労 4.7- 0% 18.9 -23.6% 
The wolframite mineral series was mineralogically studied by BROCH (1929) 
to be a continuous solid solution varying from orthorhombic FeW04， s=90000'， 1:0 
monoclinic Mn W04 with a s angle of 90053'. According to him， the gradual 
increase of the ao， bo， and Co lattice parameters and the increase in the angle s 
seem to correspond with increasing of Mn content. 
BERMAN and CAMPBELL (1957) studied the relationship of composition to ther-
mal stability in the wolframite mineral series and also gave the methods for 
determining the MnO content by the precise measurements of (200) and (030) 
spaclngs. 
TAKANO (1957) also examined the relationships between lattice parameters 
and chemical composition on some specimens from Japan. 
Recently， SASAKI (1959) has examined the variation of unit cell parameters of 
this mineral series on the synthesized specimens and some chemically analysed 
natural specimens， and clariiied that ao， bo， and Co increase almost linearly with 
increasing MIlo content as follows :from Go=4.732A，bo=5.707Aand co=4.965A 
in FeW04 to ao=4.834A， bo=5.758A and co=4.999A in MnW04・ Hisresults 
also showed that angle s varies gradual1y from 90000' in FeW04 to 9101' in 
MnW04・
3. . 'Fhe mode of occurrence of ferberite from the Ashio copper mine 
The ore deposits of the Ashio copper mine occur both in the Ashio rhyolitic 
body and in the Paleozoic chert bed. The deposits consist of two types， veins and 
massive replacement or widely disseminated deposits. The veins occur chiefly 
in the' Ashio rhyolitic body， IDut also in the Paleozoic chert bed. On the other 
hand， the massive replacement or widely disseminated deposits， which are called 
“Kajika" by miners， are especially developed in the Paleozoic chert bed and also 
found in the Ashio rhyolitic body. 
め Feγbeγite01 the ceγztγal Sγz-W-Bi-Cu zone in the Ashioγ均olzticboの
As described in the previous paper (NAKAMURA， 1954， 1961) the distribution 
of metals， Sn.W.Bi.Cu.Pb.Zn etc.， and the mineral parageneses in the deposits 
show a considerable variation in the individual vein， but also in the district as a 
whole. 
Cop.sidering the area occupied by the Ashio rhyolitic body as a whole， three 
hypogene mineral zones are distinguished both horizontally and vertically: (i) a 
central Sn-W-Bi-Cu zone， (ii) an intermediate Cu-As-Zn zone， and (ii) a mar-
Some Characteristic Features 01 Ferberite from the Ashio Co妙 erMine， Jaρan 3 
ginal Zn-Pb-Cu-As zone. Ferberite occurs in the cassiterite-bearing quartz vein 
in the central S1il-W -Bi-Cu zone. 
The central Sn-W -Bi-Cu zone is characterized by the presence of high-grade 
Sn-Cu ore (more than 1% Sn) and the high-temperature mineral parageneses. 
Tin bonanza is chiefly restricted in the higher mine-levels (above the 13th level) 
in the Ashio rhyolitic body. Frequently， the thin platy or slender needle fer-
berite， U. 3mm. to O. 5mm. long and O. 02mm. to O. 05mm. thick， occurs in close 
association with a col1oform variety of cassiterite，“wood tinぺ
Sometimes， in the lower mine-levels of the central Sn-W-Bi-Cu zone， the 
thin tabular ferberite， 5mm. to 1cm. long and O. 5mm. to 1mm. thick， isscattered 
in the quartz vein with small amounts of chalcopyrite and pyrite. Under the 
microscope very small fibrous aggregates of cassiterite are observable in this 
q uartz vein. 
From the sequence of mineralization ferberite was formed simultaneously 
with or slightly later than cassiterite. 
b) Fe，ybe，yもte01 the "Kajika" detosits iγt the Paleozoic cheγt bed 
Ferberite rarely occurs from the “Kajika" deposi ts in the Paleozoic chert bed. 
It is also closely associated with cassiterite. 
4. Mineralogical properties of ferberite from the Ashio copper mine 
a) S.ρecimen analysed 
The analysed ferberite specimen was taken from the upper sub-6th level of 
the 200・shakuvein in the Yokomabu-higashi・10・icross-cut in the upper 6th leve1. 
In th'e 200・shakuvein， the thin tabular ferberite， 5mm. to 1cm. long and O. 5mm. 
to 1mm. thick， of which chemical and X-ray studies were made， isscattered in the 
quartz vein with small amounts of chalcopyrite and pyrite. Under the micro-
scope， small grains of cassiterite are scattered in the quartz vein. The wall-
rock su妊ersstrong silicification and sericitization. 
Ferberite-rich part picked up with pincette was crushed and sized， the minus 
100-， plus 200・fractionbeing retained. Then， ferberite was separated by means 
of bromoform. It was then ready for further mineralogical investigations. The 
material used for chemical analysis was fairly free from impurities. 
的 Chemicalcomtosition 
The result of chemical analysis is shown in Table 2. 
From the chemical analysis， the chemical formula of this mineral was expres-
sed as (Feo・96MnO・04) W04・ Thisis very close to the Fe-end member of the 
ferberite species. 
Furthermore， this mineral was examined semiquantitatively by means of 
the fluorescent X-ray spectrographic methods. Comparing the intensity of FeKf3 
(20=51.730) with that of MnK，β(20ニ 56.62")，the value of 1 (FcKs) 11 (MnKs) is 
approximately 14. The fluoresent X-ray spectrographic data also clarified this 
mineral to be the ferberite with a composition near the Fe-end member. 
， 
、4 Takeshi N'，AKAMUlRA 
Table 2. Chemical composition of feroerite from the Ashio copper mine. 
Weight % Mol. prop. W03，=I 
W03， 75.95 % 3275 1.00 
FeO 22.49 3.130 
MnO 0.98 138 0.04 
Ca() 0.08 14 
MgO O.04 10 
F 
Total 99.54 
(Analysit: 1'1. NAKAMURA) 
c) x-γ仰 dzlf;γactio悦 dαtα
The X-ray diffraction data obtained by Phirlips Nore~cü diffractometer are shoWJl 
in Table 3. lndexing of refl.ections was made in terms of t>eing orth@rnombic. 
Table 3. X-ray powder diffractioJil data of ferber抗ef rom the As!hio copper mine. 
ao=4733A，bo=5.707A，ICo=41.967A 
The experimenta】conditionsare as follows: Nιnltered Cu radiation， 35k V， 10mA， scann-
ing speed 10(28) and 10 /4 (2，fJ) per miaute， time constant 4 seconds， receiving slit 0.006 inches， 
angular aperture 10， and goniometer radius 170mm. 
Some Characte.γistic F eatu:γes 01 Ferbe:γite f;γom the Ashio Co争μγ Mine.Ja似悦 そ
Unit cell parameters determined by the measurements of (030)， (200)， (020)， 
(111)， (110)， and (011) spacings are shown as follows: 
ao=4.733A， bo==5. 7'07 A， co==4. 967 A， and s==90000'. 
Calculated density is 7.516 g j cm3• 
5. Characteristic features of the wolframite mineral series from 
the subvolcanic hydrothermal deposits in Japan 
On the mineral features of the wolframite mineral series from various types 
of Bolivian deposits， AHLFELD (1936) suggested that only with high-temperature 
formation in pegmatitic and hypothermal phase al1 members of this mineral 
series (except those rich in Mn) are formed; further he noticed that with 
decreasing temperature of formation a gap in mixtures occurs， so that in the 
mesothermal and epithermal deposits members rich in Fe or those rich in Mn 
are formed. 
KHASIN (1949) and LEUTWEIN (1952) suggested that the proportions of Mn to 
Fe in this mineral series are control1ed by the temperature of formation， Mn-rich 
wolframite being deposited at higher temperatures. 
EDWARDS and LYON (1957) clarified that analyses of wolframite sample from 
localities selected so as to cover the full range in depth and lateral extent of the 
Aberfoyle mine， .Tasmania， show no simple relationship between Mn content and 
depth. However， according to them， the composition of the wolframite is about 
intermediate of the ferberite-huebnerite series at the Aberfoyle mine. 
In Japan the wolframite mineral series occur both from the subvolcanic hydro-
thermal deposits and from the plutonic hydrothermal deposits including pegma-
titic deposits. The atomic ratios of Fej (Fe+ Mn) of this mineral series from 
the subvolcanic and plutonic hydrothermal deposits in Japan are shown in Table 4. 
Seeing from the value of Fej(Fe+Mn)， itis clear that both ferberites and 
huebnerites generally occur in the subvolcanic hydrothermal deposits， and that 
wolframites of intermediate composition chiefiy occur in the plutonic hydrothermal 
deposits including pegmatitic deposits， although alI members of the wolframite 
mineral series occur in the plutonic type deposits. 
Seeing from the mode of occurrence， the ferberite crystal from the subvolcanic 
hydrothermal deposits， such as those of Akenobe， Ikuno and Ashio， shows a thin 
platy or slender needle habit and further it is genetically closely associated with 
the colloform variety of cassiterite，“wood tin". The huebnerite crystal from 
the subvolcanic hydrothermal deposits， such as those of Ikuno and Nishizawa， 
also shows a thin platy or slender needle habit. On the other hand， the wol-
framite from the plutonic hydrothermal deposits including pegmatitic deposits， 
such as those of Kaneuchi and Takatori， occurs as a large tabular crystal. 
As shown above， there is a marked contrast in the mineralogical features of 
the wolframite mineral series between those from the subvolcanic hydrothermal 
deposits and those from the plutonic hydrothermal deposits. A thin ρlaかorslender 
γzeedle feγbeγite 0γhuebγzeγite closel-ヲ αssociatedwith a collofoγm 包aγietヲ 01cαssi-
terite is a characteγistic mineγal 01 the subvolcanic均dγotheγnalde会ositsz'n J atan. 
The mode of occurrence and mineralogical properties of the wolframite mineral 
series are very interesting from the view point of ore genesis. 
6 Takeshi NAKAMURA 
Table 4. The value of Fej(Fe+Mn) in the wolframite mineral series fr0m Japan. 
Locality 
Nishizawa mine， *)Tochigi Prefec-
ture 
Gessei， Kaneuchi mine， **) Kyoto 
P refecture 
Takatori mine， **) lbaragi 
Prefecture 
Y omei， Kaneuchi mine， **) K yoto 
P refecture 
Nishizawa mine， *)Tochigi 
Prefecture 
Funai， Kaneuchi mine，料)Kyoto 
Prefecture 
Akenobe mine， *)Hyogo 
Prefecture 
Ashio mine， *) Tochigi 
Prefecture 
Otomezaka mine，**) Yamanashi 
Prefecture 
Frej (Fe+ Mn) 
(atomic ratios) 
0.13 
0.35 
0.48 
0.54 
0.71 
0.73 
0.96 
0.96 
0.96 
????????????
Huebnerite 
Wolframite 
Wolframite 
Wolframite 
Wolframite 
Wolfrarnite 
Ferberite 
Ferberite 
Ferberite 
Analyst 
KAvVAKITA (1908) 
HARAMURA (1959) 
KOZAKI (1927) 
HARAMURA (1959) 
WATANABE (1908) 
HARAMURA (1959) 
KOZAKI (1927) 
NAKAMURA (1959) 
KODERA (1915) 
*) Subvolcanic hydrothermal deposits. 
**) Plutonic hydrothermal deposits including pegmatitic deposits. 
Besides， Huebnerite (Fej(Fe+Mn)=0.05) was reported from the quartz vein (plutonic type) 
cutting through the bedded manganese deposits in the Paleozoic formation at the Hagidaira 
mine， Gunma Preiecture (SASAKI， 1959). Huebnerite also occurs frorn the manganese 
deposits at the Kaso mine， Tochigi Prefecture (KATO， 1959) and the ReNge mine， Yamaguchi 
Prefecture (LEE， 1955). 
The thin platy or slender needle ferberite and huebnerite also occur from the lkuno mine， 
Hyogo Prefecture (ITo and SAKURAI， 1947). 
、
References 
AHLFELD， F. (1936) : The Bolivian tin belt， Econ. Geol.， vol. 31， pp. 48-72'. 
BERMAN， J.， and CAMPBELL， W.J. (1957): Relationship of composition to thermal stability in 
the huemnerite-feriberite series of tung，states， U .S. Bureau of Mines" Rept. of Invest. 
5300. 
BROCH， N. A. (1929) : Norsk. Ak. Oslo. Math. -Nat. KL Skrifter 8: PALACHE， C. BERMAN， H. 
FRONDEL， C. ; The system of mineralogy， vol. 2， p. 1065 (1951). 
ED'A'ARDS， A. B.， and LVON_， R. J. P. (1957): Mineralization at Aberfoyle tin mine， Rossarden， 
Tasmania， Proc. Aus. Inst. Min. Met.， No. 181， pp. 93-145. 
ITo， T. and SAKURAI， K. (1947) : Wada's minerals of Japan， 3rd Ed. (in Japanese). 
KATrαA. (1958): Huebnerite from the Kaso mine， Tochigi Prefecture， Jour. Miner. Soc. 
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KHASIN， R. A. (1949): On the zonality of the isomorphous series ferberite-huebnerite in 
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LEE， D. E. (1955) : Mineralogy of some japanese manganese ores， Stanford Univ. Publications 
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LEUT¥¥'EIN， F. (1952) : Die chemische Zusammensetzung der Wolframit und ihre lagerstatten-
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、
4・
(1951): The sys色emof mineralogy， vol. 2， pp. 
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Some Characteristic Features of Ferberite from the Ashio copper Mine, Japan : Studies on Minerals from the Ashio Copper Mine, Japan II

On Some Characteristic Mineralogical Features of Chlorite from the Ashio Copper Mine, Japan : Studies on Minerals from the Ashio Copper Mine, Japan I.

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Some Characteristic Features of Ferberite from the Ashio copper Mine, Japan : Studies on Minerals from the Ashio Copper Mine, Japan II

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