Art and Culture
Plantage buurt

Gassan Diamonds

Art and Culture / Plantage buurt
Nieuwe Uilenburgerstraat 173 - 175

“On the 29th of June a new GEBR steam diamond mill was built in the Uilenburgerstraat. BOAS opened, of a particularly large size and for 357 mills. Made entirely of iron, these are set in motion by two horizontal steam engines, system SULTZER, each with 40 horsepower. For purchase of land and building of the plant, machines, boilers, etc., a sum of fl. 400.000, – was claimed. All the mills were soon occupied, and the factory now has 357 sharpeners, 122 adjusters, 142 pupils and 52 errand boys. Weekly an average of 8 to 10,000 carats of rough diamonds was cut, valued approximately from 500,000 guilders to 500,000 guilders, which for the most part was provided by the owners themselves. ”

From: Report Chamber of Commerce 1880. Municipality Archive Amsterdam.

The construction of the diamond factory of the Boas brothers had not gone unnoticed. The new plant was the largest in this area across Europe. In the press, the building was described with general admiration and amazement as a modern wonder of technical ingenuity. The imposing building, with the spacious forecourt, must have contrasted with the immediate surroundings: in those days Uilenburg was still a ghetto with a jumble of narrow alleys and corridors and a multitude of slums. Who were these Gebr. Boas who had the guts to start such a business in this neighborhood?

The Boas family

Grandfather Marcus Abraham Boas lived in the Rapenburgerstraat in 1812 and was “Oud Kleerekoper”. His son Juda Boas became a shoemaker and married Betje Groenteman in 1838. They had 7 children: 4 girls and 3 boys, Israel, Marcus and Hartog.

Israel and Marcus left for Paris at a young age. Paris was then the center for the diamond trade. How is not clear, but the suspicion seems justified that the Boas brothers learned the diamond profession there.

The factory

Around 1870 a business cooperation between the three brothers arose: Hartog ran the factory in Amsterdam; Israel and Marcus bought the rough diamonds in London and sold the cut product in Paris. Around 1870 Hartog Boas lived and worked on the Nieuwe Keizersgracht no. 16. During the “Cape period” – a golden period for the Amsterdam diamond industry – the company grew out of the building. With bits and pieces, heirs were bought between the Uilenburgerstraat, the Houtkopersburgwal and the Uilenburgergracht. In 1878 the tender followed by the architect and mechanical engineer J.C. Meyer. The building was completed in 1879. Even now it is said that the Gebrs. Boas were out of the costs within a year, which should certainly be considered possible given the productivity stated by the Chamber of Commerce.

Messrs. Boas tow diamonds for their own account. From the guest book of the factory it appears that the customers from the first day came from far and wide to buy bricks at the Gebroeders. They came from all over Europe, even from the United States, from Russia and Japan.

The Union

Attracting workers in this neighborhood, where unemployment was high, will not have been a problem for Hartog Boas. However, the trade unions were less happy with the new company. They warned against the unbridled influx into a profession that was so heavily subject to economic fluctuations. The warnings were in vain, in fact, some trade unions were almost empty because of the arrival of the factory. Due to the enormous supply of workers, wages fell. The Gebrs. Boas and the trade unions have been each other’s opponents for years.

Absent Gentlemen

In 1894, Hartog Boas started TBC, a common disease among diamond workers. He left behind a young family with 6 children. Israel and Marcus remained – unmarried – in Paris. The factory was led by an agent. The brothers – now in their forties – were able to retire at that moment, not a bad result for sons of a shoemaker !!

As uncles, Israel and Marcus had good contact with the children of their brother, witnessed an intensive correspondence between Paris and Amsterdam. It is striking that the factory is not mentioned in any of these letters. Hartog’s children did not opt ​​for the diamond profession: Julius Hartog retired; Marcus Israël became a neurologist and Bernard studied philosophy in Munich. The girls also married “outside the diamond trade”. Israel took over the management of the factory in 1935, after the death of “Uncle Marcus”. He has lived mainly in France and in Switzerland. The day-to-day management remained in the hands of an agent.


The factory continued to expand and innovate, both in organization and in construction. From 1890 on, fewer and fewer were sharpened for their own account. They switched to the system of letting of grinders to independent diamond dealers. In 1894/95, in the major strikes that led to the establishment of the General Dutch Diamond Workers Union, the ANDB, the Gebr. Boas no longer referred to as patrons. In 1921 a definitive change was passed on to the Commercial register: “Steam diamond grinding Gebr. Boas, rental of diamond mills. In the 1920s, the factory was still steaming, even though electricity had come during the First World War, reportedly laid by fled Belgians. During this period, the diamond trade’s revenues were very volatile. The major economic crisis of the 1930s was the final death blow for a number of diamond companies. Many diamond workers moved to Antwerp to try their luck there. In the large Boas building, other industries were a textile trade, a stocking factory, a slipper factory, a paint factory. During the war, the factory was requisitioned by the Germans who tried to keep the diamond industry running. When it did not work, the Boas factory was liquidated in 1944. Marcus Boas and his family were able to move to the United States in time. Bertha Boas left for England with her sons in 1939 and Bernard Boas was safely escaped to Switzerland. Martha, Julius and Elisabeth died in concentration camps. The decay and a new start After the war, the building complex led to a languishing existence, and became a plaything for project developers and municipal zoning plans. Once a year, Marcus I. Boas came over for a few days to deal with his business here and to look at the Factory again. He died in 1986 at the age of 94. His daughters sold their “last part” of the building complex to Gassan in the summer of 1989. This started a new episode in an “Old Factory”, because with the Gassan company the Diamonds have returned to Uilenburg.

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