Rock formation.—Mineral deposits.—Gold.—Copper.—Iron.-Coal.—Silver.—Salt—Building stone.—Petroleum.—Mineral springs.—Earthquakes.

The geological formation and the mineral wealth of the Dominican Republic have never been thoroughly studied, in part because of the physical difficulties and in part as a result of the civil dissensions. The government has never had money to spare for such objects, and private investigators have suffered much hardship and lost many days in opening paths through tangled underbrush, and in crossing rugged mountain ranges in uninhabited regions. The physical obstacles and the necessarily superficial examination consequent thereon may explain the contradictions of detail in different reports. About the middle of the nineteenth century several studies were published, and three scientists who accompanied the American Commission of Inquiry in the year 1871 made a report on geological conditions.

From such studies as have been published it appears that the rock formations of Santo Domingo correspond to the secondary, the lower and middle tertiary and the quaternary epoch. The most ancient part of the island is the central mountain range, also a series of protuberances in the Samana peninsula, the nucleus of the Baboruco mountains and a single point in the northern coast range near Puerto Plata. The tertiary lands are those forming the entire northern part of the island from the central range to the sea, portions of the Samana peninsula between the older rocks, a large area to the southwest of the Zamba hills, smaller tracts between the Jaina and Nizao rivers, and the region between the salt lakes on the Haitian frontier and between Barahona and Neiba. The modern lands are the coast plains and the small terraces on the south of the central range and on the south of the Baboruco mountains, the Maguana, Azua and Neiba valleys, small areas on the north coast at the foot of the mountains, and the marshes and Yuna River delta at the head of Samana Bay.

In the central mountain range is found a nucleus of eruptive rocks which have raised and twisted sedimentary strata, covering them and forcing them aside. This nucleus is not a regular feature of the whole length of the chain, but is an irregular mass beginning about at the middle, in the region of the Jaina River, and extending in a series of parallel lines obliquely across the backbone of the range to the border of the Republic and on into Haiti. Among these rocks and bent and broken by them are the slates, conglomerates and calcareous rocks which are found in the mountains and over the whole surface of the island. The character of the central range and the inclination of the strata of cretaceous rocks make it probable that the island emerged from the sea in the eocene period, its area being then confined to the extent of the central mountain chain, with a few small islands to the south, one or more islets to the northeast, comprising the older peaks of the Samana range, and a small archipelago to the southeast, where the hills of Seibo now are. During the miocene period these islands became surrounded with coral reefs, the vestiges of which remain in strips of calcareous rock found in the same position in which they were deposited. Towards the end of the tertiary period, after a time of quiet, there was a new rise of the land. While the hills to the south of Samana Bay and the bed of the Cibao Valley from Samana Bay to Monte Cristi rose slowly, there was an upheaval further to the north, and the Monte Cristi Range was formed. Before this period it had been a bar at sea-level, covered with a clayey sediment of chalk. At a later geological period the great plains to the north and east of Santo Domingo City were formed.

Traces of valuable minerals are so general in the Republic that it is said there is hardly a commune where a more or less abundant mineral deposit is not found. The exceptions are the lands of recent coralline formation, such as the municipality of San Pedro de Macoris and the southern portion of the commune of Higuey.

The magnet which attracted the Spaniards at the time of the conquest was the island's mineral wealth, especially the gold deposits. It is a historical fact that large quantities of gold in dust and nuggets were collected during the first years of Spanish colonization. According to the Spanish writers, from 1502 to 1530 placer gold was produced to the value of from $200,000 to $1,000,000 per annum. The fleet which set out in 1502 and was wrecked by a hurricane before leaving the coast waters of Santo Domingo was laden with gold mined in the island. A tribute of a small amount of gold each year was imposed on half the Indians of the country. Much of the gold came from the mountains behind Santiago and La Vega, from the gold-bearing sands of the Jaina River, around Buenaventura, and from the vicinity of Cotui, then called "Las Minas." Ancient pits are still to be found in all these places. At La Vega a mint was established for coining gold and silver. A nugget of extraordinary size was found by an Indian woman in a brook near the Jaina River; her Spanish masters in their exultation had a roast suckling pig served on it, boasting that never had the king of Spain dined from so valuable a table. The Indian received no part of the gold: "she was lucky if they gave her a piece of the pig," remarks Father Las Casas. This nugget was purchased by Bobadilla to send to Spain, and went down with the 1502 treasure fleet.

The gold deposits found by the Spaniards were the surface accumulations of centuries. When these were exhausted and the supply of cheap labor fell off owing to the dying out of the Indians, the mineral production waned. In 1502 labor difficulties caused a temporary cessation in mining. In 1511 many mines were definitely closed because of the scarcity of laborers and because the cultivation of sugar-cane offered surer profits. Then came the discovery of mines of fabulous wealth in Mexico and Peru, and the interest they aroused, as well as the lack of labor in Santo Domingo, caused the mines of the island to be completely neglected. Finally, in 1543, mining work ceased and by a royal decree all mines were ordered closed. Prospecting and desultory mining, especially placer mining, have been kept up, however, until the present day.

The prospecting has generally been confined to the more accessible regions and nothing is known of the mountain valleys in the interior. The mineral deposits discovered have been of sufficient richness to cause the formation of mining companies for their development or further investigation. I do not, however, know of a single case where prospectors or mining companies have ever made expenses. The cause of failure has most frequently been the lack of transportation facilities in the island, on account of which the cost of carrying the ore to a place where it might be reduced became prohibitive. Sometimes enterprises failed because the deposit turned out to be too small, sometimes because the ore did not keep up to the standard, and not infrequently mining companies fell by the wayside because of bad management. Enough evidence of mineral wealth has been found to justify the belief that workable deposits do exist, and to warrant careful further investigation, especially as the means of communication are extended.

The metals most frequently found are gold, copper and iron. Veins of auriferous quartz are found throughout the central chain, the richest lodes being encountered in metamorphic rocks near crystalline formations. The metal is most abundant in placers formed in the river beds. Such placers are common in the Jaina River and its tributaries in the province of Santo Domingo; in Bonao creek in Seibo province; and in the Verde River, the streams of Sabaneta and a number of other streams of the Cibao. On the upper Jaina and on the Verde River there are still persons who make their living by washing gold from the river sands. Hydraulic mining was attempted in Santiago province, but after the construction of an expensive canal the project was abandoned. Under the liberal mining law mining privileges have in recent years been granted for gold mines reported at numerous places in the communes of San Jose de las Matas, San Cristobal, Janico, San Juan de la Maguana, Sabaneta and others. Prof. William P. Black, one of the scientists accompanying the United States Commission of Inquiry in 1871, reported:

"There is a very considerable extent of gold-bearing country in the interior and gold is washed from the rivers at various points. It is found along the Jaina, upon the Verde, and upon the Yaque and its tributaries, and doubtless upon the large rivers of the interior. Some portions of the gold fields were worked anciently by the Spaniards and Indians. There are doubtless many gold deposits, not only along the bed of rivers, but on the hills, which have never been worked, and there probably is considerable gold remaining among the old workings. The appearance of the soil and rocks is such as to justify the labor and expense of carefully prospecting the gold region."

Copper is next to gold in frequency of occurrence. Some of the best deposits have been found in the commune of San Cristobal, province of Santo Domingo. A company working lodes at Mount Mateo on the Nigua River, encountered ore yielding as high as 33 per cent of copper. On the Jaina River near the ruins of Buenaventura, I have seen promising ledges of copper ore. Copper carbonates predominated, the green ore known as malachite and the beautiful blue ore azurite were quite common, and white quartz, which on being broken showed little specks of native copper, was also to be found. The asperity of the region, the absence of roads and the uncertainty as to the extent of these deposits caused the attempts at working them to be but feeble until recently, when extensive works of development were undertaken in the vicinity. Copper veins have also been reported in the mountains of the commune of Bani, province of Santo Domingo; in the communes of Cotui and Bonao, province of La Vega; in the canton of Moncion, province of Monte Cristi; in the commune of San Juan de la Maguana, province of Azua, and at a number of other places.

Iron is reported in large quantities in various parts of the country. The largest deposit so far known is on the banks of the Maimon River in the municipality of Cotui, being a bed of black magnetic oxide of iron, nine miles long. It is said to be excellent in quality and inexhaustible in quantity. The difficulties of transportation in this case could be obviated by the canalization of the river to its confluence with the Yuna River, so as to make it navigable for small boats. Iron ore has been discovered on the slope of Mt. Isabel de Torres behind the city of Puerto Plata, limonite deposits at various places in Santo Domingo province, and a rich black iron oxide on the upper Ozama River. A layer of iron pyrites extending from Los Llanos all the way to Sabana la Mar was believed by its discoverers to be a gold mine. The central ridge of Santo Domingo is part of the same mountain chain which extends through Santiago province in Cuba where enormous quantities of iron are produced, and it is not improbable that some of the Dominican mines will be found to pay.

Coal mines found in the Samana peninsula produced a kind of lignite which proved of little commercial value and gave rise to the belief that the Republic's coal deposits had not emerged from the formative period. Later investigations show that while there is considerable undeveloped lignite, coal suitable for fuel is not wanting. Small coal deposits have been discovered in the Cibao Valley, between the central and the northern mountain chain, in the province of Pacificador and that of Santiago. Anthracite coal found at Tamboril, near the city of Santiago, was used to run a small motor exhibited at an industrial fair in Santiago in 1903. In the commune of Altamira, province of Puerto Plata, lignite and anthracite beds have been discovered, and traces of anthracite have also been found in San Cristobal commune, and in the petroleum region of Azua. In the central mountain chain a valuable coal deposit has been found on the Haitian side and similar beds may be expected in Santo Domingo.

Silver has been discovered at Tanci, near YÁsica, in the commune of Puerto Plata. The old chronicles refer to silver mines at Jarabacoa and Cotui in La Vega province, also to others near Santiago, near Higuey and on the Jaina River. Platinum occurs at Jarabacoa, traces of quicksilver have been found near Santiago, Banica and San Cristobal, and tin in Seibo and Higuey.

Rock salt is found near Neiba in inexhaustible quantities, there being several hills of native salt covered with a thin layer of soil. The fact that the waters of Lake Enriquillo are saltier than the sea is attributed by some to a deposit of this kind. The salt is so pure that it does not attract moisture and deliquesce. The isolation of the district has been an obstacle to the development of the salt mines, but there is a project for the building of a railroad to the port of Barahona. Part of the salt used in the island comes from salt ponds near Azua, where salt is obtained from sea water by solar evaporation.

On a hill at the confluence of the Jimenoa and the Yaque del Norte an alum deposit reaches the surface and the natives gather alum which they sell in Santiago City. A deposit of amber having been reported in the Cibao a company was formed several years ago for its development, but as the company did nothing, so far as known, except issue stock, and no part of the untold millions which were affirmed to be within easy reach has materialized, the deposit is not regarded as possessing commercial value.

For building purposes there is a large variety of limestone and lime. The coral rock is easy to quarry and soft enough to shape with the axe, but exposure to the air makes it hard as granite, as is proven by the old buildings and city walls of Santo Domingo City, which have stood for centuries. In the central range, on the Samana peninsula and near Puerto Plata, granite, syenite and other building stones are found, but owing to the absence of transportation facilities they are not utilized. In the Bani region a sandstone occurs from which grindstones are made. Clay of a fine grade, proper for the manufacture of bricks and tiles, is abundant. Clays of various colors, found in the interior of the island, are suitable for the manufacture of paints. Gypsum is found, especially in Azua province, and the presence of kaolin and feldspar in the province of Santo Domingo, south of the central range, offers a possibility of porcelain manufacture.

Petroleum has been found in large quantities in the vicinity of Azua. The presence of the oil is suspected in other parts of the island and it is claimed that a petroleum belt which is believed to extend from Pennsylvania to Venezuela embraces a considerable portion of the Dominican Republic. Near Puerto Plata, during rains, one of the streams flowing down from the mountains in the Mameyes section, is covered with greasy spots thought to be petroleum that has oozed from the subsoil. Traces of petroleum have also been discovered near Neiba, and in the provinces of Pacificador and Seibo.

Borings have been made only in the neighborhood of Azua. A pool known as "agua hedionda," "stinking water," had long suggested petroleum, and an American company known as the West Indies Petroleum Mining and Export Company undertook the development of the field. Oil was struck on November 14, 1904, the well spouting oil to a height of seventy feet and producing about 500 barrels per day. The grade of the oil was 22 Baume gravity with an asphaltum base. It was better than the average of Texas oil and was considered a good fuel and lubricating product. The main difficulty in this field was the presence of salt water above the oil (as is often the case in oil regions), which here came in rapidly at a depth of about 900 to 1000 feet. It was necessary to put a gate valve on the first well, keeping it enclosed for a period of six months, in order to prevent the damaging of the surrounding property from the flow of oil, as there were no storage tanks. During this time the continued agitation of the casing by the gas pressure and the looseness of the upper soils and shales let in the salt water and ruined the well, and, it is to be feared, to some extent affected the surrounding territory. The company sunk four wells more, all but one of which produced some oil, but as the salt water entered in such large quantities they were unable to penetrate below the 1200 feet level and were forced to abandon the wells at just about the depth where they expected to reach the real oil sand. The fifth well showed greater evidence of a genuine oil field than any drilled previously but for the same reason it could not be carried to the desired depth. At this point dissensions arose in the management of the company with regard to the method of drilling, the suggestion being made that a combination drilling machinery comprising what is known as the rotary process be adopted in combination with the old cable rig style. No agreement was reached, and operations were discontinued. Since the beginning of 1917 other interests have made investigations and it is rumored that development work will shortly begin. There are indications that if drilled with the proper appliances the field will yield excellent results. How far the Azua oil field extends is a matter of conjecture, but it has been estimated to cover an area of over 190 square miles.

Thermal springs are also found near Azua. At Resoli, about 21 miles southwest of Azua City, there are hot sulphur springs of very copious flow. Nearby there is one of tepid water, slightly acid and stinging, though pleasant to the taste, and with no trace of sulphur. Within a radius of a hundred yards there are about a dozen springs of different temperatures and medicinal properties, and the place is admirably adapted for the location of a health resort. Mineral springs, especially sulphur springs, abound along the western frontier of the Republic. On the Viajama River, where a sulphur mine is reported, there are cold sulphur springs which are said to have gushed forth for the first time during the earthquake of 1751. To the east of Santiago are the Anibaje springs which contain sulphur and iron. Hot and cold sulphur springs are found in the outskirts of San JosÉ de las Matas, southwest of Santiago, and hot springs at Banica, and to the east and west of Lake Enriquillo.

While there are no volcanoes on the island, severe seismic disturbances have at times occasioned great havoc and loss of life. One of the first and most memorable was that of 1564 which overthrew the cities of La Vega and Santiago de los Caballeros. La Vega was at that time a good sized town with substantial brick houses, and the masses of masonry strewn about in the thicket which now covers the site of the old city give evidence of the force of the earthquake. In 1654 and 1673 dwellings and churches in Santo Domingo City were damaged by lesser shocks, and in 1751 an earthquake wrecked edifices in the capital, and completely destroyed the old city of Azua and the town of Seibo. The most recent and perhaps the most disastrous earthquake was that of 1842 when a violent commotion in the northern part of the island demolished the cities of Santiago de los Caballeros on the Dominican side and Cape Haitien on the Haitian side, bringing death to hundreds of their inhabitants. Since that date there have been no severe shocks, though, as is the case in other West India Islands, slight tremblings of the earth are not infrequent. I have experienced several of such tremblings in Santo Domingo and have never been able to ward off a kind of creepy feeling when the rattling of windows and doors indicated their approach and passage. Near the ruins of ancient La Vega the natives point out a spot in the woods which they call "tembladera" and where they say the earth quakes at the approach of man. Investigation discloses that while the earth really does tremble when anyone walks at this place the cause is not so deep-seated as many imagine, the phenomenon being caused by the fact that the rich loamy soil is sustained by the interlaced roots of trees, the foundation having been washed away by subterranean waters, and the grassy floor is swayed by every motion upon it.