much silica. One of the most considerable and interesting occurrences is
that of Oberneisen, where the hæmatite appears in contact with the "Lahn
porphyry" the best-grade ore here contains 65 per cent. of metallic iron.
Then there are the iron and manganese-ores associated with the dolomitized
Stringocephalus-limestone, the hummocky surface of which forms the floor or
hanging-wall. These oft-described and much discussed deposits often pene-
trate deep into fissures and hollows of the underlying limestone, and are
mantled by a barren cover of drift-sands and clays of varying thickness. The
ore-bodies range in thickness from 20 to 40 feet, and lumps of pure psilo-
melane and pyrolusite are distributed through the crumbly hæmatite. It
is noticeable that the more highly fissured and dolomitized the limestone is,
the richer and more abundant are the ores. One of the most important
mines that work these deposits is situated in the Lindner Mark, south of
Giessen: the extensive workings here are opencast. Borings to the north
and south have proved vast masses of still unworked ore of excellent quality.
Between Nauheim and Homburg-vor-der-Höhe are the manganese-mines
of Oberrossbach and Köppern, where shafts have been put down to a depth
of 213 feet, and workable ore still remains below this. The ore contains
from 18 to 22 per cent. of manganese, 27 to 33 per cent. of iron, 0-3 to 0:4 per
cent. of phosphorus, and 8 to 9 per cent. of residues. But it is much richer in
manganese at the outcrop, and this holds good also (in regard to iron) of
the accompanying brown hæmatite. A brief description of the not dissimilar
ore-deposits of Weiler-West, Bingerbrück, Waldalgesheim, and the Bieberthal
is also given, and the author then proceeds to consider the question of their
origin. He regards many of them as primarily the result of weathering
(decomposition of rocks by atmospheric agencies) but does not exclude the
occasional intervention of ferruginous and manganiferous thermal springs;
and he points out that the Nassau deposits (at all events) are generally
regarded as having been formed by such springs and in no other way.

Brown coal is of frequent occurrence in the Tertiary deposits along the slopes of the Taunus; but in some places the quality, and in others the quantity, of the mineral is apparently not sufficient to justify working. However, about 118,000 tons of brown coal were got in the year 1900, the best being the Pliocene coals of the Friedberg district. The older (Oligocene) coals are much poorer. The quantity of workable brown coal still in sight is estimated at 15,000,000 tons.

Elaborate statistics are tabulated of the mineral output of the Wiesbaden and Koblenz districts and of the Grand Duchy of Hesse during the past six years. L. L. B.

THE MAGNETITE-DEPOSIT OF THE SCHWARZER KRUX, THURINGIA,
Das Magneteisenerzlager vom Schwarzen Krux bei Schmiedefeld im Thüringer Wald.
By KARL SCHLEGEL, Zeitschrift der Deutschen Geologischen Gesellschaft,
1902, vol. liv., pages 24-55, with 3 text-figures, and plates II. and III.
The magnetite-deposits of the Schwarzer Krux, near Schmiedefeld, were
worked for many centuries, and then abandoned in the latter half of the
nineteenth century. Somewhere about 1888 an attempt was made to restart
mining operations, but it was a purely spasmodic effort, and now the work-
ings have fallen in the enormous waste-heaps scattered through the forest
alone bearing witness to the activity of former generations of miners.

A brief sketch is given of the literature of the subject, and the author

then describes the granite-massif on which the Schwarzer Krux is situated. This granite is presumed to date from Carboniferous times, while the sedimentaries through which it has torn its way are of Upper Cambrian age. The rock is of two varieties-typical biotite-granite and two-mica-granite : both varieties contain tourmaline. Quartz-porphyry dykes course through the granite-massif, and the granites themselves are full of inclusions of quartz-mica rock and hornblende-schist.

The waste-heaps really contain vast quantities of iron-ore which will be industrially available, so soon as the projected railway from Ilmenau to Schmiedefeld is completed. As in the case of the granites, etc., the author made an elaborate petrographical study of the magnetite, examining many scores of microscopic slides. The ore varies considerably in structure from compact, through finely granular, to coarsely crystalline: sometimes it shows traces of schistosity. Fluorspar is invariably associated with it: frequent associates also are wolframite, molybdenite, barytes and pyrites. An analysis of "magnetite-rock" yielded 88.55 per cent. of iron oxides and 9.10 per cent. of manganese oxide.

The ore occurs near the contact with the granite in the metamorphosed clay-slates, and apparently is itself really a metamorphosed hæmatite-deposit. Similar examples, due to contact-metamorphism, are cited from Spitzenberg in the Harz and Angers in the west of France. The fluorspar is no doubt the result of fluoric emanations which would make their way through the fissures in the rocks caused by the irruption of the granite. The occurrence of a garnet-rock rich in fragments of crystalline limestone also points to the former existence of limestone-bands in this locality. L. L. B.

THE ORE-DEPOSITS OF THE MÜSEN DISTRICT, GERMANY. Der Schichtenaufbau des Müsener Bergbandistriktes; die daselbst auftretenden Gänge und die Beziehungen derselben zu den wichtigsten Gesteinen und Schichtenstörungen. By MAX BROCHER. Verhandlungen des naturhistorischen Vereins der Preussischen Rheinlande, etc., 1902, vol. lix., pages 99-134, with 5 text-figures and plates II.-III.

The area in question comprizes various groups of high hill-ranges which form a portion of the Siegerland, and all the strata are of Lower Devonian age. They consist of an alternation of grauwackés, grauwacké-slates and clay-slates, all striking uniformly north-east and south-west, and dipping south-eastward at high angles (from 30° to 80°). The bedding is not especially massive, and stratigraphical units approaching or exceeding 160 feet in thickness are of rare occurrence. A detailed description is given of the highly-jointed grauwackés, and of the other strata already mentioned, but a group peculiar to the Müsen district is that of the Red Slates, interbanded at various horizons with the other rocks. They are very flaggy. splintery, and fairly hard (5 in the scale of hardness). Their brown-red coloration is doubtless due to the 10 per cent. or so of iron peroxide which they contain, and moreover that peroxide appears to be the material which has bound the other constituents of the slates together. Taken as a whole, the strata show signs of considerable disturbance and faulting, and the author describes at length the two main fissure-faults of the district: the Stuff and the St. Jakobskluft.

The ore-deposits are defined as independent lenticular veins, showing

great variations when compared one with the other. The author divides them into two categories:-(1) Ironstone-veins, the ore in which is mainly spathose iron and the gangue mainly quartz; and (2) ore-veins proper, containing sulphides of lead, zinc, silver and copper, with heavy-spar as the commonest gangue. At the outcrop, the metallic sulphides are frequently found decomposed to oxides and hydroxides. The veins in some cases represent the infilling of fissures which have been torn in the rocks without any intervention of lateral thrust. In other cases, they are the infilling of true fault-fissures, and in yet others they are genetically connected with overthrust-phenomena.

A short description is given of the most important ore-deposits. In the first place, as regards the iron-ores the Brücher vein, 10 feet thick, has been now worked out, and the same statement holds good of the Stahlberg deposit. The Sonnenberg, Kuhlenberg and Jungermann veins have been worked as far as it would pay, and are now abandoned.

Galena and zinc-blende are got from the Glücksanfang veins Nos. I. and II.; the ores apparently increase in richness and quantity the deeper down they are worked. Similar ores, with, in some cases, fahlores and copperpyrites, are worked from about a dozen other veins. In the diagonal vein" there are masses of pure ore 10 feet thick, and the entire ore-body is in places as much as 33 feet thick.

The ore-deposits are invariably cut off or nipped out by the Red Slates: these were in a relatively plastic condition at the time when fissures were being torn in the other rocks, so that fissures could not remain open in them to receive the metalliferous infilling. Later on the now Red Slates were infiltrated with the iron peroxide which has cemented them together. Generally speaking, there is cumulative evidence of a relationship between the fault-folds of the district and the metalliferous veins, as the number, thickness, and character of the latter have been unmistakably influenced by the former. It may be added that the sulphidic ores are very probably of more recent date than the iron-ores in the Müsen district.

L. L. B.

THE IRON-ORE DEPOSITS IN THE WESER HILLS, WESTPHALIA. Die nutzbaren Eisensteinlagerstätten, insbesondere das Vorkommen von oolithischem Rotheisenstein, im Wesergebirge bei Minden. By DR. TH. WIESE. Zeitschrift

für praktische Geologie, 1903, vol. xi., pages 217-231, with 2 figures in the text. At one time clay-ironstones alone were got in the Weser Hills, near Minden in Westphalia, but of late the winning of hæmatite has taken the front rank. It occurs in the Jurassic strata, in the neighbourhood of the famous Porta Westphalica, and the mines are connected by a light railway with the main line from Cologne to Minden. Clay-ironstones are still worked in the Wittekind seam, near Bergkirchen, and in the reniform concretions of the Bockshorn gravel-pit at Veltheim-on-the-Weser.

A description, geological and physiographical, of the Weser range of hills, based on Prof. Romer's and Dr. Heinrich Credner's monographs, is given by the author. It may be noted in passing that the Wittekind seam is a marly iron-pisolite in the Lower Kelloways rock, dipping near Bergkirchen some 30 to 40 degrees, 3 feet thick, overlain by a band of pyrites which in places is as much as 6 feet thick, and is in turn overlain by 8 inches more of pisolite. At Lutter, the pisolite is 6 feet thick. The ore contains, on an average, 30 per cent. of metallic iron.

Then follows a detailed description of the " seams" of red hæmatite which occur among the Upper Oxfordian limestones. At the Victoria mine, the lowest ore-band is called the Nammer-Klippen seam; it is oolitic in structure, and contains in its upper portion rather more than 22 per cent. of metallic iron: the total thickness of the seam varies between 33 and 40 feet. An interval of some 3 or 4 feet of blue limestone separates it from the next overlying seam, the Victoria, 6 feet thick, containing about 40 per cent. (on an average) of metallic iron. Working was started on this seam in 1884, and it is now practically exhausted. Above this follows more blue limestone, 30 feet thick, and then the Joseph hæmatite-seam, in composition and appearance much like the Victoria seam. But, though analyses showed it to contain from 58 to 61 per cent. of iron peroxide, it proved unworkable, as it thinned out so rapidly. The Lower Kimmeridge limestones and marls form the cover.

At Kleinenbremen, the following hæmatite-seams are recognized, in ascending order: (1) Nammer-Klippen seam, 13 feet thick, containing from 15 to 25 per cent. of metallic iron, as yet unworked; and (2) Wolverwahrt seam (with which among other minerals an anthracitic pyritous coal is associated), 4 feet or so thick, containing in choice samples 46 per cent. or more of metallic iron, and 0:11 per cent. of phosphorus, the average content of iron being from 38 to 40 per cent. This seam continues in depth to the west, but nips out in depth eastward.

66

The local designation of seams is, the author remarks, perhaps in fact hardly applicable to all of these hæmatite-deposits, although they are conformably interbedded with the strata among which they occur, and both as to roof and floor, sharply marked off from them. Microscopic examination shows that the minute structure of the deposits is truly oolitic, and they are in this and in other respects comparable with the Clinton ores. They were laid down in sea-water: so much is proved by the palæontological evidence. He concludes that they originated in the same fashion as the minettes or oolitic iron-ores of Luxemburg and Lorraine: iron-salts in solution, brought into the sea by springs or rivers, underwent a series of chemical reactions, the final result of which was the precipitation of the iron in the form of oxides and oxyhydrates.

L. L. B.

THE BARYTES-DEPOSITS OF THE RÖSTEBERG, NORTHERN

GERMANY.

Die Schwerspathvorkommen am Rösteberge und ihre Beziehung zum Spaltennetz der Oberharzer Erzgänge. By H. EVERDING. Zeitschrift für praktische Geologie, 1903, vol. xi., pages 89-106, with 11 figures in the text.

The Rösteberg (1,175 feet above sea-level) is the highest summit of a ridge which marks the boundary between the Palæozoic massif of the Harz mountains and the Mesozoic foot-hills, in the district that lies between Grund and Gittelde. The barytes occurs in apparently-bedded deposits of Permian age forming the very top of the Rösteberg; and a hundred feet or so away, in the Paleozoic slates is the old Hülfe Gottes (God's Help) metalliferous mine, which was worked for many generations. The remarkable occurrence of the Rösteberg crops up again and again in the scientific literature dealing with the Harz, a short summary of which is given. After a fairly-detailed description of the barytes-deposits as seen in several small

quarries opened up to work it, the author proceeds to consider the vexed question of its origin. All the evidence that he can adduce points to its genesis through metasomatic replacement of the Zechstein Limestone, brought about by the active circulation of thermal waters carrying barium, etc., in solution.

It has been shown that pure barytes is being formed in certain Westphalian collieries at the present day, by the interaction of pit-waters, some containing barium salts and the others sulphates in solution, and this is in localities where the Carboniferous is much disturbed by cross-faulting. The Rösteberg mineral is in truth genetically connected with the faultfissures, some of which in the immediate neighbourhood were infilled with metalliferous ores; and this faulting probably originated at the same time and from the same causes, both within and without the orographic boundary of the Harz massif. But the Rösteberg faults are at any rate post-Permian, since the Permian strata have been disturbed by them; therefore, too, all the metalliferous veins of the Upper Harz are post-Permian (including the God's Help vein). The long process of mountain-building, in the case of the Harz, may well have lasted from the close of the Devonian into Tertiary times. Whether the metalliferous veins occupy fissures first formed during the latest movements, or whether these fissures really date back to the earlier movements, and were continued and re-opened by the later, is a point still in dispute. L. L. B.

ORIGIN OF THE PYRITES-DEPOSITS OF RAMMELSBERG, GERMANY,
Ueber merkwürdige Einschlüsse im Kieslager des Rammelsbergs bei Goslar.

By

ALFRED BERGEAT. Zeitschrift für praktische Geologie, 1902, vol. x., pages
289-293, with 2 figures in the text.

In contradistinction to Prof. Vogt's view that the Rammelsberg ore-body
is of the nature of a vein-deposit, the author holds that it cannot possibly
be anything else than a true bedded deposit, which was formed contem-
poraneously with the Wissenbach slates and is a member of that series
of strata. In support of this opinion he adduces fresh evidence in the shape
of masses of iron-pyrites, smooth and reniform, which occur amid the so-
called mixed ore (alternating bands of fine grained chalcopyrite and
galena) of Rammelsberg; these are unmistakably concretions formed within
a sedimentary bed, and would of themselves be sufficient to dispel the notion
(if it were otherwise admissible) that the pyrites-deposits near Goslar were the
outcome of the metasomatic replacement of limestone.
L. L. B.

PRECIOUS OPAL OF DILLENBURG, GERMANY.

Opal in der Gegend von Dillenburg.

By

LÖCKE

Zeitschrift für praktische

Geologie, 1903, vol. xi., page 303. The author recently discovered precious opal in a freshly opened exposure of eruptive diabase on the right bank of the Irrschelde valley, 24 miles northeast of the village of Oberscheld, in the district of Dillenburg (Nassau).

The mineral occurs in bluish to milk-white lumps, varying in size from that of a hazelnut to that of a walnut, in small "nests in the diabase, sometimes intergrown with red hæmatite. The opal showed conchoidal fracture and (in places) most brilliant iridescence.

In some cases crystalline quartz was associated with it.

L. L. B.