the main goods exported from the colony to the Netherlands until the early 18th century, when coffee became the single most important export product of Surinam. Planters' treatment of the slaves was notoriously bad. The historian C.R. Boxer wrote that "man's inhumanity to man just about reached its limits in Surinam", and many slaves escaped the plantations. The Amsterdam Stock Exchange crashed in 1773, which dealt a severe blow to the plantation economy that was further exacerbated by the British abolition of the slave trade in 1807. This abolition was adopted by William I of the Netherlands, who signed a royal decree in this regard in June 1814, and who concluded the Anglo-Dutch Slave Trade Treaty in May 1818. Many plantations went bankrupt as a consequence of the abolition of slave trade. Without supply of slaves, many plantations were merged to increase efficiency. Abolition of slavery Slavery was eventually abolished on 1 July 1863, although slaves were only released after a ten-year transitory period in 1873. This spurred the immigration of indentured labourers from British India, after a treaty to that effect had been signed between the Netherlands and the United Kingdom in 1870. Apart from immigration from British India, Javanese workers from the Dutch East Indies were also contracted to work on plantations in Surinam. At the same time, a largely unsuccessful attempt to colonize Surinam with impoverished farmers from the Netherlands was started as well. The natural resources of Suriname In the 20th century, the natural resources of Surinam, which include rubber, gold and bauxite, were exploited. The gold rush that followed the discovery of gold on the banks of the Lawa River spurred the construction of the Lawa Railway in 1902, although construction was halted after gold production proved disappointing. In the 1930s, the grandmother of Hennah Draaibaar discovered more than 80 kilos of gold, which made her briefly the richest woman in Surinam; the Dutch took most of the gold to the Netherlands. In 1916, the U.S. aluminium company Alcoa began mining bauxite on the banks of the Cottica River, near the village of Moengo. In 1938, the company built an aluminium smelter in Paranam. The 1930s were a difficult time for Suriname. The Great Depression created great unemployment. Surinamese guest workers in Curaçao and other islands of the Netherlands Antilles returned to Suriname because there was no more work, which exacerbated the problem. No more