First Report On The Geology And Mineral Resources Of British Somaliland With Map

10. BARITE

Barite was found in two places in Bihendula Range: (1) In a small tug on the north-east margin of the gneissic mass just below the sandstone, which forms the base of a small outcrop of Jurassic limestone in contact with Daban conglomerates. (2) On the motor road from Berbera to the Bihendula rest-house, in a gorge below the hill called Ardah about two miles north-west of the rest-house, and one-eighth of a mile to the south-east of the track.

(1) In the small tug on the northeast margin of the gneiss, the mineral occurs in foliated hornblende gneiss, along joint planes, cracks, or what are perhaps slip zones, in veins from 1 1/2 inches to 1 1/2 feet in thickness. The foliation of the gneiss strikes N. 18° W., and pink and white felspar pegmatite veins and dykes run parallel with this foliation. The similarity between some of these pegmatite veins and those of the barite may lead to the occurrence of the latter being missed unless the high specific gravity of the barite is kept in mind. The veins of the mineral, in contrast with the pegmatite, run in a direction W. 10° N.-E. 10° S., and the slip planes along which the mineral occurs appear to dip 60° in a north-westerly direction. There appears to be plenty of barite in the locality, floaters being found all along the tug, but, as the veins disappear under the gritty Jurassic sandstone, it was not possible to ascertain how far they extend along the strike.

(2) In the gorge below Ardah, occurs a large vein of barite, composed in places of three bands each nine inches thick, but mostly of one band about two feet thick. The vein can be traced for 200 yards up the hill in a south-easterly direction from the gorge, and for 100 yards in a north-westerly direction towards the motor track. There are a fair number of floaters on the camel track and in the gorge and the tug. The mineral occurs in a gray granitic or slightly hornblendic gneiss in which are numerous joint planes at right angles to the foliation of the gneiss, the strike of which is N. 36° E., or virtually north-east—south-west. The trend of the vein, on the other hand, is N. 40° W., or virtually north-west—south-east.

The barite fills a crack or fissure or joint-plane in the gneiss. Though a small fault has bent the course of the vein at one point, there does not appear to have been any considerable faulting in the neighborhood, and it is improbable that the crack or fissure marks a fault-plane. On the other hand, as the joint planes in the gneiss run in a direction N. 40° W., i.e. , that in which the vein itself runs, it is most probable that the mineral occupies a joint plane.

The barite is white, in places with a slight pinkish tint, and appears to be very pure. An analysis of a typical specimen made at the Imperial Institute gave these results:

According to the report accompanying the details of the analysis, the sample was of good white color when finely ground, and material of similar quality would probably be suitable for purposes to which ground barite is generally applied.

The sample was, of course, only a surface one, and it is possible that the amount of lime contained in it may be smaller in material from greater depths.

There is little doubt that other veins of the mineral occur in this range and could be found with little trouble.

11. CELESTITE

This mineral was first recognized by the writer in Ferrio Range, about a mile west of Gebilay Well, in a small outcrop of yellow shales forming part of the Gypsum Series that overlies the Eocene limestone and forming the bank of a small tug. Subsequently, it was found in greater or less amount in every ridge on which the Gypsum Series was present, and there is no doubt that it occurs everywhere in these yellow shales. Near Gebilay, the celestite is in small masses of translucent white crystals which have hitherto probably been mistaken for gypsum.

The chief deposit met with, however, was on the west side of the saddle between Himbir Yer and Himbir Wein tugs, on the main track from Hebah Las to Gerfoleh in Ferrio Range. The mineral there formed an outcrop on the surface, of several square yards in extent but of unknown depth, composed of crystals of size up to three inches square. There must be many other similar masses to be found both in this range and in the Gypsum Series on Al Wein Range.

An analysis of samples from near Gebilay and from the saddle near Himbir Wein made at the Imperial Institute gave the following proportions:

According to the report accompanying the results, the samples were of good white color when finely ground, and material of similar quality would probably be suitable for the purposes to which ground celestite is generally applied, though it is doubtful whether supplies of the mineral from Somaliland could be profitably disposed of on the English market in competition with the material obtained in the United Kingdom.

In parts of Ferrio Range, occasional crystals of a blue, somewhat fibrous variety of the mineral are met with, and in the banks of Dudub tug, between Las Dureh and Hodmo tug, large round aggregates of circular crystals occur in the Eocene limestone.

12. MOLYBDENITE

This mineral was found in rocks in Dobo Tug about a quarter of a mile up the tug from Dobo Well, near Wobleh Range in the Gadabursi country. Wobleh Range itself consists of coarse and fine-grained granitic gneiss with dykes of pink, of white, and of pink-and-white granite pegmatite. The molybdenite occurs in splashes and nests in the pink-and-white pegmatite. Only one dyke containing the mineral was encountered, and only a small amount of the mineral was found in it, but as, owing to considerations of time and the roughness of the country, it was not possible to examine more than a few pegmatites, a further search of the neighborhood would probably result in the discovery of other occurrences. A considerable improvement, however, on the present state of the communications between Dobo and either Zeyla or Hargeisa would be necessary before any deposit could be exploited.

13. GYPSUM (MASSIVE, SELENITE AND SATIN-SPAR)

Gypsum deposits of very large extent and thickness have been found in different parts of the Protectorate, particularly in the Guban, on the eastern portion of the high plateau, and in the south-eastern district from Kirrit eastwards. The chief localities are: the southern slopes of Al Wein Range, about sixteen miles south-east of Berbera; the southern slopes of Ferrio Range, about ten miles south-east of Al Wein Range; the neighborhood of Las Dureh, Dodab and Las Adey; the hills and tugs in the east of the plateau from Dabbar Dalol and El Afweina to Erigavo and Jid Ali, and probably as far as the eastern boundary; between Biji and Bia Bolgashan on the Kabal-Kabat track, north-east of Hargeisa and south of Bulhar.

The mineral occurs in three forms:

1. 1. 1. Massive gypsum, associated with anhydrite.
      2. Selenite and Satin-Spar.
      3. Alabaster.

1. Almost the whole of the gypsum in the Protectorate occurs in the massive form, but the two chief deposits are those forming the uppermost beds of Al Wein Range and Ferrio Range. The gypsum of Al Wein, which covers all the southern slopes, is probably quite 2,000 feet thick, and dips conformably with the Eocene limestones underlying it. The slopes are deeply intersected by ravines, the sides, and floor of which are all formed of the mineral. The gypsum is commonly of a greyish or yellowish-grey hue. In places, however, are white streaks, patches and small blocks surrounded by the greyish material, and on the floor of some of the tugs in Al Wein, a more or less gradual passage of the white into the grey mineral can be traced. Analysis at the Imperial Institute of a sample of the white mineral from Agagwein Ridge gave the following results:

Calculation, from this analysis, of the amount of gypsum (CaSO₄, 2H₂O) present shows that, assuming all the H₂O to be present in gypsum, only 21.5 percent of gypsum is present in the sample. The remainder of the CaSO₄, amounting to 73.3 percent, is, therefore, in all probability present as anhydrite. Results of specific gravity tests on specimens composed of both the white and grey material, and evidence of a gradual passage of the white mineral into the grey strongly support this conclusion. Indeed, it is most likely that all the gypsum was originally in the form of anhydrite, but has been transformed by exposure to air and moisture.

The gypsum of Ferrio Range occurs in exactly the same manner and is of approximately the same thickness as that at Al Wein. In the neighborhood of Las Dureh, Dodab and Las Adey, it forms the surface of the fairly level ground, but is seamed by ravines, many of which are fifty feet deep with walls and floor wholly of the mineral.

2. Selenite and Satin-Spar. Selenite occurs as thin bands in the massive gypsum, in great amount in the shales and sandy shales of the Daban Series near Khal Der, and, in a state of great purity, in the massive gypsum walls of Dodab tug. Nowhere, however, were any large homogeneous deposits of it encountered, though many tons of it could be collected from Khal Der, where it occurs in plates about a foot square and up to an inch thick on the surface of the shale outcrops.

Satin-Spar, or fibrous gypsum, occurs in the same manner as selenite as veins up to a foot in thickness in all the outcrops of massive gypsum, and veins of this variety are especially common on Al Wein, and in Dodab tug.

Both varieties are common in very thin plates in the clay shales of the Upper Eocene, and even in the kerogenous shales of the Jurassic at Meragelleh.

3. Alabaster.—Large deposits of this variety, exceeding twenty feet in thickness, were met with at Dabbar Dalol Well, about seven miles south of El Afweina, in the east of the Protectorate. The material occurs in slabs measuring from one foot to two feet square and from three inches to six inches thick. It is fairly pure, and of a dead-white color on the exposed surface and when rubbed.

Another deposit at least twenty feet thick and extending along a tug for at least half-a-mile occurs at Dodab. The mineral is greyish-white in color and shows a more or less distinct veining.

The prospects of the deposits from an industrial standpoint are, for the present, at any rate, scarcely worth considering. Except in the case of the deposit on Al Wein, the cost of transport of the material to a port or even to any place where a factory could be established, would, in view of the low market value of the material, effectually prevent it being worked successfully, and it is fairly certain that, though the Al Wein deposit is sufficiently near Berbera to present no difficulties as regards transport, it would not be profitable to export gypsum from it to European or other overseas markets.

Should, however, agriculture be seriously attempted in the Protectorate, the finely-ground pure material may be of use locally as a fertilizer.

14. GOLD

In Vol. XVI of the Peace Handbooks,^[18] the question of the occurrence of gold in British Somaliland is dealt with in these terms:

“Statements are to be met with, especially in older accounts of the country, to the effect that goldfields exist in British Somaliland.

“It has been suggested that the gold-producing district, known to the ancient Ethiopian Empire as Sasu, may be located in the north-east corner of Somaliland, stretching southwards in the direction of Obbia in Italian Somaliland. Attempts have also been made to prove that the gold-bearing country known to the ancient Egyptians as Punt is identical with these parts of Somaliland. There is, however, no evidence of the existence of goldfields in the country. The ranges of the Somali hinterland are Archaean gneisses, schists and granites, but, notwithstanding their resemblance to Egypt, they do not, so far as is known, furnish auriferous deposits.”

In the Military Report on Somaliland, and in the Military Handbook on Abyssinia, the statement is made that both alluvial gold and gold in quartz occur in the Protectorate, and, on an official file in Berbera, is a statement that a sample of gold in quartz obtained in Somaliland was taken to Delagoa Bay in 1903. No mention, however, is made of the locality from which these specimens are alleged to have been obtained, nor is there any official record of their discovery.

Particular attention was paid by the writer to the possibility of finding this mineral, and, though no gold was found in situ or in the gravels and sands collected, two districts were met with in which, from the nature of the rocks and the character of the quartz, its occurrence might be expected. These were:

1. 1. 1. The slate country south-east of Las Gori, in the Warsangeli district, in the north-east of the Protectorate.
      2. The country a little west of Borama and in the vicinity of Halissa and Dehraweina.

1. The series of slates is seamed with veins and reefs of quartz, many of them several feet thick. The quartz is usually ferruginous with a cellular or porous structure due to the decomposition, probably, of iron pyrites, and, therefore, of a character which, in the light of experience elsewhere, must be regarded as favorable for the occurrence of gold. Time did not allow of the sampling of more than a very few of the veins and of the stream sands, and, though no gold was found in those examined nor was any visible gold met with in the veins and reefs, yet, in view of the great extent of the slate country, the great number of quartz reefs, and the fact that even in a proved gold-bearing country, gold does not occur in all the reefs, there is some prospect of the discovery of the mineral in this district, and it warrants careful prospecting. That these black slates are the rocks in which galena also is found in British territory and probably galena and cinnabar in Italian territory renders the district all the more worthy of special attention.

An assay of a sample obtained from a quartz reef near the galena occurrence at Unkah, but showing no galena whatever, gave:

From this result it would seem that though the sample was of no value in itself, yet the reef is to some extent argentiferous and may be auriferous.

In view of the presence of the numerous ferruginous reefs and veins, a special interest, therefore, attaches to past attempts to reconcile this north-eastern part of the Protectorate with the Sasu region of the Ethiopian Empire. The Somalis themselves are firmly of opinion that gold has been obtained in it, though the justification for their opinion could not be elicited.

2. The country near Borama and in the vicinity of Debraweina appears also to be worth prospecting. On the trek from Somadu to Borama, the writer was impressed with the possibility of the occurrence of gold in the district south of Dorjibis, which is only a few miles north and north-east of Debraweina.

A sample taken from a small tug at Dorjibis, assayed at the Imperial Institute, gave:

Another sample, of sand, taken from the bank of Amud Tug, east of Borama, gave:

In the report on the results of the assays, the Institute remarks that most of them are of interest as indicating the presence of gold in the localities from which they were obtained.

Moreover, about a fortnight before the writer left the Protectorate, he accidentally came across amongst the official files an old volume in which was a letter from a Colonel Ashby, containing the statement that he had found gold in 1900 (or 1901) in the Debraweina district and that he had had numerous coolies working on the occurrence. Apparently, as was the case in other connections, the unrest arising from the operations of the Mad Mullah caused the abandonment of the work. It is clear, however, that he must have discovered some valuable mineral in promising quantity, for otherwise, he would scarcely have had a large number of coolies at work on the occurrence. It is regrettable that no access could be had to this letter in time to allow of an examination of the locality. At the time of its discovery, the period of the tour had ended.

In the light, then, of the statements in the letter, and of the finding of apparently favorable country a few miles to the north of Debraweina, there can be no doubt that the prospects of the tract outlined are sufficient to warrant a careful and intelligent search of it for precious metals.

15. CLAY

Owing to native rumors of the occurrence of soapstone near Bayal Well, north of Bihendula Range, a Somali who knew the occurrence was sent by the writer to collect specimens of it for examination. The material brought in consisted of fragments and round lumps of a pale grey and of a pale green color, which, both in appearance, hardness and feel, closely resembled soapstone. Blowpipe examination, however, showed it to be not soapstone but an aluminum silicate. Subsequent reference to the records of the Imperial Institute showed that samples of this substance had been analyzed in 1920, with the following results:

These results indicate that the composition of the clay is nearly the same as that of montmorillonite. Tests carried out at the Institute show that it would not be suitable for the manufacture of pottery or bricks, as any article made from it cracks badly on drying. Its particular importance lies in the fact that, when ground, it is a clay which, according to the Imperial Institute, could be used satisfactorily as a clarifier in oil refining, and, having regard to the possibilities of the petroleum seepage at Dagaha Shabell, the occurrence, therefore, merits being placed on record. The material forms part of two small hills near Bayal Well, about twenty miles south-east of Berbera.

Up to the present, no clays of commercial value other than the above have been found. Yellowish clays do occur as bands in the Jurassic limestone and some whitish clay-shales were met with in the Abassa Tug near Abassa Dadera, but, even if they were of value in themselves as an ingredient of cement, the general inaccessibility of the localities in which they occur would render them of little practical importance. It is possible, however, that there are clays interbedded with the Eocene and Coastal limestones which could be used profitably in the manufacture of cement and attention should continue to be directed to their discovery.

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