BAUXITE IN ITALY.

Der Bauxit in Italien. By VITTORIO NOVARESE.

Geologie, 1903, vol. xi., pages 299-301.

Zeitschrift für praktische

Bauxite has been vainly sought for many years in Calabria. In 1900, great masses of it were discovered by mere chance, at several localities in the Central Apennines, and the discovery was published by Prof. Mattirolo in May, 1901.

The Central Apennines consist mainly of huge massifs of Mesozoic limestone, ranging uninterruptedly in age from the Trias to the Upper Chalk and capped by the Eocene Nummulitic limestone. The bauxite occurs among the Urgonian or Caprotina-limestones (Cretaceous), at practically the same horizon as the bauxite in Southern France, in very extensive beds varying in thickness from 34 to 26 feet. The mineral varies in colour from deep brownish-red to yellowish-red, light-pink or cream, is soft or crumbly, heavy (specific gravity 2.95 to 3.45), and of a peculiar pisolitic structure. The pisolitic spherules range in diameter from 0.04 to 0:40 inch. The mineral is evidently of the same age as the limestone-beds among which it is intercalated. Five analyses of the bauxite (from Lecce dei Marsi, Pietraroja, Pescosolido and Rocca di Mezzo) are tabulated, showing the percentages of alumina to vary from 47:44 to 58.85, and of iron sesquioxide from 1862 to 36-37. Silica and titanium oxide are invariably present, but only one sample yielded phosphorus pentoxide (0.02). The Italian bauxite is rich in titanium, like some of the French bauxites and is easily attacked by sulphuric acid.

The author describes the deposits of Lecce dei Marsi and Pescosolido, both of which localities are favourably situated in regard to transportfacilities. They are practically untouched so far, only some preliminary exploration-work having been done on them-sufficient, however, to show that there is enough mineral in sight to supply the whole of Europe for many years to come. L. L. B.

CINNABAR-DEPOSITS OF MONTE AMIATA, TUSCANY.

(1) Sulla probabile Esistenza di un Giacimento Cinabrifero nei Calcari Liasici pressoAbbadia San Salvatore (Monte Amiata). By B. LOTTI. Bollettino del Reale Comitato Geologico d'Italia, 1901, vol. xxxii., pages 206-215, with 1 figure in the text.

For more than 50 years the innumerable fragments of cinnabar disseminated in the detritic deposits which occupy a long belt of ground near Abbadia San Salvatore have stimulated prospectors to search for the original locus of the ore. These researches have been lately systematized, with the result of arriving at what is no longer a mere probability, but a practical certainty, in regard to the site of the cinnabar-deposits.

A detailed description is given of the stratigraphical succession in this In descending order, it is as follows:-

area.

9. Pliocene marine shelly clays and sands.

8. Upper Eocene shales and marly limestones (with the latter, at Il Siele and Le Solforate, are intercalated clays containing cinnabar). Euphotides and other serpentine-rocks are associated with these.

7. Eocene sandstones, occurring in lenticular and wedge-like masses, occasionally dovetailed with the overlying limestones.

6. Nummulitic limestone, interbedded with red and grey clays,

5. Argillaceous shales and red and grey fucoidal limestones, alternating with reddish calcareous breccias (containing fishes' teeth) and manganiferous shales. Probably in part Lower Eocene and in part Upper Cretaceous.

4. Senonian limestones and shales, with manganiferous beds.

3. Upper Liassic shales of various colours, underlain by

2. Shales and cinnabar-bearing limestones, also belonging to the Upper Lias.

1. Middle and Lower Liassic limestones, passing in places into gypsum

beds.

Exploration-work has shown the chief cinnabar-deposit so far known below Monte Amiata to occur in a "chaotic mass beneath a trachytic sill, 165 feet thick, which is itself overlain at Lame by a lacustrine deposit. Speaking generally, both the Eocene and Mesozoic formations hereabouts are ridged up into anticlines. The metalliferous (cinnabar-bearing) clays and sands occur also in the lake-bed above the trachyte, which itself has undergone dislocation, fissuring and slipping. It seems probable that all these cinnabar-bearing beds are the secondary stage of pre-existing deposits, and that the primary origin of them is connected with the emanations of sulphuretted hydrogen (puttizze) and the sulphureous thermal springs so common in this portion of the Monte-Amiata massif. The author thinks that more important cinnabar-deposits than those yet touched will be found in the Upper Liassic rocks of the district.

(2) Das Zinnobervorkommen am Monte Amiata, Toskana. By VINCENZ SPIREK. Zeitschrift für praktische Geologie, 1902, vol. x., pages 297-299.

In 1897, the author explained the results to which a prolonged study of these deposits had led him, in so far as their genesis is concerned. An acid solution of sulphates of mercury, iron, and other metals invaded the argillaceous limestones, whether of Liassic or Eocene age, and the subsequent chemical reactions, especially if hydrogen sulphide were present, favoured the formation of compounds of sulphur with calcium and the alkalies, causing the mercury to be precipitated from the now neutral solution in the form of red, crystalline cinnabar. This mineral variety can be originated only in the presence of highly sulphidic alkalies or alkaline earths in neutral or alkaline solutions, otherwise the sulphide of mercury appears. as a black amorphous precipitate.

it.

The argillaceous constituents of the limestone formed a sort of protective crust around the cinnabar, shielding it from re-solution, and in the hollows of the limestone, pyrites and selenite were also deposited in company with At a subsequent period, waters charged with carbonic acid enlarged the old and formed new hollows in the limestone, and the cinnabar was redeposited, this time in association with calespar; or, in those cases where the neighbouring rocks are of a porous character (trachytes, sandstones, etc.) the cinnabar was actually carried away by the circulating waters. It occurs also as an impregnation in the most recent travertines.

The author's views have been confirmed by the researches of Mr. B. Lotti, one of the principal officers of the Italian Geological Survey, and by the observations of Mr. F. Amman, who manages the newly-opened mine of Abbadia San Salvatore.

The point that remains to be determined is the source of the sulphuric acid metalliferous solutions. They are evidently associated with the eruptive magma which formed the diabases and serpentines of the district.

(3) Il Monte Amiata. By A. VERRI. Bollettino della Società geologica Italiana, 1903, vol. xxii., pages 9-39, with 1 text-figure and plate II.

After a description of the Mesozoic and Tertiary sedimentaries which overspread the country around the central mountain-mass, the author devotes some pages to the volcanic rocks (largely rhyolites and trachytes) of which Monte Amiata itself is built up. He takes the opportunity of describing also the neighbouring volcanic mass of Radicofani, the mere remnant of a great basaltic eruption. Both that cone and Monte Amiata stood up possibly as islands in the later Pliocene sea, the volcanic phenomena dating perhaps precisely from that period. The moribund phase of vulcanicity is represented in the neighbourhood by numerous thermal springs, some of which are sulphureous, others ferruginous and highly charged with carbonic acid.

The cinnabar appears to be impartially distributed among the Mesozoic sedimentaries (Cornacchino mine); the Eocene marls, etc. (Siele and Solforate mines); the Eocene sandstones and Nummulitic limestones (Montebuono and Cortevecchia mines); the Pliocene sedimentaries (Saturina mine); and even among the trachytes and the overlying lacustrine deposits. It was worked by the ancient Etruscans, who used the ore simply as colouringmatter, and again in mediæval times (from 1200 to 1300). Wars and plagues decimated the country, and the mineral-industry was not revived there until 1846. In 1901, the mines of Abbadia, Cornacchino, Siele, Solforate, etc., were being actively worked, and the total output amounted to 278 tons of metallic mercury, the average yield of metal from the ore being 774 parts per thousand. Native mercury sometimes occurs in drops" with the cinnabar, and the other associates are iron-pyrites, gypsum (both amorphous and crystalline), calcite, and rarely quartz. At Selvena, stibine also occurs, while at San Martino cinnabar is found in an antimony-mine. The richest ore occurs in pipes (or pockets) of clay or sand among marly and other limestones.

The author summarizes the various opinions expressed by a succession of writers, from 1850 to 1903, as to the origin of the cinnabar-deposits. With differences as to detail, all are agreed that the genesis of these deposits is undoubtedly connected, directly or indirectly, with the volcanic phenomena of the neighbourhood. L. L. B.

THE BOGHEAD OF RESIUTTA, ITALY. Resiutta: Cenni su quello Schisto bituminoso (Boghead).

ANON. [16 page

pamphlet published by G. Smerzi e C., Venice, 1901.] The bituminous shale of Resiutta occurs about 3,300 feet above sea-level, and 2,600 feet above the Pontebbana railway-line, among (perhaps strati graphically below?) the Triassic strata which are the predominant sedimen tary formations of the Tagliamento river-basin. An analysis shows that it contains 47 47 per cent. of volatile matter (and water), 142 per cent. of fixed carbon, and 38:33 per cent. of ash. The percentage of sulphur is stated as 3-847, and of phosphoric anhydride in the ash 084. Distilled at high tem peratures, the "boghead" produces a gas of exceptional illuminating-power. At lower temperatures it gives rise to a whole series of coal-tar products, and heavy and light oils. The specific gravity of the mineral is 3:12.

Experiments made by the City-of-Venice Gas Company showed that the distillation of the Resiutta boghead furnishes a gas which may be used either by itself as an illuminant, or for enriching or carburetting ordinary

gas in the latter case the addition of a very small percentage of it produces a relatively considerable effect. The coke obtained from this boghead is of no value as a fuel, but if ground to powder it is available for bleaching and disinfecting purposes. L. L. B.

LIGNITES OF THE VICENTINO, NORTHERN ITALY.

Di alcuni Giacimenti lignitiferi del Vicentino. By T. TARAMELLI. Giornale di Geologia pratica, 1903, vol. i., pages 141-144.

The author agrees with Dr. Dal Lago in considering that the Eocene lignites which crop out at several localities in the province of Vicenza are not derived from peat, but from vegetable débris (trunks, branches and leaves) drifted into and accumulated in the lakes and estuaries of the early Tertiary period. He mentions, by the way, the bituminous lignites of Zovencedo and Monteviale, which yield but a small output and that of poor quality. These are of Oligocene age.

The most important deposits of the province lie among the hills through which the Agno, the Chiampo, the Alpone, the Illasi, and their affluents have cut their way. In the valley of the first-named a basalt-flow may be seen underlying the oldest Eocene, while elsewhere the Tertiary sedimentaries are traversed by intrusive dykes of later eruption. The oldest lignite-deposit in the region known to the author, that of Monte Pulli, rests upon Alveolinalimestones with intercalations of shelly bituminous marl. The mineral contains much sulphur, was first worked in 1841, and is once more the object of mining operations, although the deposit is not such as to admit of working on a very extensive scale.

Two beds of lignite have been traced in the neighbourhood of Castelvecchio, west of the Val d'Agno. Exploration-work in the commune of Cerealto has revealed other deposits, too thin to repay systematic working. The author visited a great many exposures of lignite, some of which were worked for a time, and then abandoned, and he concludes that, on the whole, the Monte Pulli deposits alone show promise of continuous remunerative working. The most recent statistics as to the annual output of lignites and bituminous schists in the province of Vicenza fix the amount at about 11,000 tons. L. L. B.

THE ORE-DEPOSITS OF BROSSO AND TRAVERSELLA, PIEDMONT. Die Erlagerstätten von Brosso und Traversella in Piedmont, By V. NOVARESE. Zeitschrift für praktische Geologie, 1902, vol. x., pages 179-187, with 4 figures in the text.

Both these localities are in the district of Ivrea, on the margin of the Alps, near the point where the Val d'Aosta opens out into the great plain of the Po. The hills consist principally of mica-schists, in which are included numerous masses of eclogite and (though more seldom) extensive intercalations of crystalline limestones and dolomites. Between Brosso and Traversella, at the watershed which divides the Val d'Aosta from the Chiusella valley, a biotite-hornblende-diorite mass is intruded among the mica-schists, sending out numerous apophyses in the shape of small dykes or veins. that neighbourhood the greatly disturbed mica-schists are traversed by numerous fissures striking north-westward and dipping regularly northward. These fissures are undoubtedly connected with the genesis of the ore-deposits.

In

The diorites have altered the limestones by contact-metamorphism, and in parts there has been a metasomatic replacement of limestone by oxides and sulphides of iron, and, secondarily, copper-pyrites. The phenomena are comparable with those observed in the ore-deposits of the Banate, and in the contact-rocks of the Christiania district.

The author then considers the ore-occurrences in detail, dividing them into three groups, the first of which comprises the magnetic iron-ores of the Bersella valley. Mining operations began here as long ago as 1487, but the industry is now at an end, and the old workings are difficult of access. Nevertheless, attempts are being made to revive mining here. In the upper part of the valley are the pure magnetites of Montajeu and Gias del Gallo (5,300 to 5,900 feet above sea-level): the ore is associated with more or less serpentinized olivine, and occurs in the form of intercalated beds among the limestones (which are in places highly silicified). In the lower part of the valley, are the iron- and copper-ore deposits of Traversella properly so-called. They are very near to the great diorite-mass, and with the magnetite are associated numerous metallic sulphides and a host of accessory ores and minerals. But the only ores that occur in payable quantity are the ubiquitous magnetite and copper-pyrites.

The second group comprises the specular iron-ore and pyrites of Brosso. From the point of view of facilities of transport these mines are much better situated than those of the Bersella valley. Working has been carried on in the Brosso mines without interruption, from the time of the ancient Romans down to our own day. The ore-bodies are in the form of banks or beds, conformably intercalated among crystalline limestones which strike westward, and dip 30 to 40 degrees southward. The thickness of the ore, however, varies considerably, from nothing to 200 feet or so. Evidently both the specular iron and the pyrites were deposited contemporaneously, and, although they are not found intimately intergrown, intrusions of the one are frequently observed in the other. The pyrites is very pure, and shows no trace of copper. Magnetic pyrites and magnetite occur, but are not worked hereabouts. The average annual production of the Brosso mines amounts to 25,000 tons of ore.

In the third group, the author ranges the metalliferous veins, which occur as infillings of the fissures mentioned in a previous paragraph. The ores in these are invariably sulphidic, and occasionally auriferous. Such fissure-deposits are common both to Brosso and Traversella, and the gangue consists of quartz and spathose iron-ore.

There is no doubt whatever that the genesis of all the ores described in this memoir is connected with the eruption of the diorite, which took place (in all probability) subsequent to the Oligocene folding of the Alps. Metalliferous vapours and solutions arose directly or indirectly from the eruptive mass, and made their way through the limestone-rocks. These were in part dissolved and leached out, and the ores and gangue-minerals were laid down in their place. L. L. B.

THE CUPRIFEROUS DEPOSITS OF BENA DE PADRU, SARDINIA. Il Crisocolla e la Vanadinite nella Miniera Cuprifera di Bena (de) Padru presso Ozieri. By DOMENICO LOVISATO. Atti della Reale Accademia dei Lincei, 1903, series 5, Rendiconti, vol. xii., pages 81-87.

A few years ago, some curious outcrops of copper-ore were discovered at Bena de Padru, on the slopes of Monte Tramento, about a third of a