Blazing sapphires and lush emeralds drip from the necklaces, brooches and bracelets. One standout piece, the “Briolette of India,” includes a 90-carat diamond and carries a high estimate of $7.8 million.

They are among the 700 jewels from the estate of an Austrian heiress that will go on sale at Christie’s on May 3 as part of one of the largest jewelry sales in history. The auction house is predicting that jewels from the estate of Heidi Horten, the heiress who died last year, will bring in more than $150 million, surpassing the $137 million taken in during the 2011 sale of Elizabeth Taylor’s collection.

The proceeds are to benefit a charitable foundation established by Horten, whose husband, Helmut, was a German retailing billionaire whose specialty was department stores.

“It’s one of the most beautifully curated collections that will ever come up in the jewelry world,” said Anthea Peers, president of Christie’s Europe, Middle East and Africa. “This is a sale that will do an enormous amount for philanthropy. That’s important for the estate and for us.”

But the auction house has acknowledged that, in deciding to host the sale, it also had to grapple with the fact that Helmut Horten’s business empire was built atop his purchase of companies from Jews who were pressed to sell by the Nazis.

“We are aware there is a painful history,” Peers said. “We weighed that up against various factors,” she added, saying that the foundation is “a key driver of philanthropic causes.”

The Heidi Horten Foundation finances medical research and runs a museum in the heart of Vienna that features the expansive art collection she built. Several historians and the daughter of a businessman who worked for a Jewish-owned company targeted for acquisition by Helmut Horten during the Nazi era said the philanthropic benefits today are not sufficient to warrant a sales event that has the effect of obscuring the roots of the family’s fortune.

“He laid the foundations of his wealth during the Third Reich by acquiring companies on the cheap at fire-sale prices from Jewish business owners under duress,” said David de Jong, the author of a recent book on Nazi billionaires. De Jong said that in several instances, such as the 1936 purchase of the Alsberg department store in Duisburg, Germany, Horten had paid no more than 65 percent of the company’s value.

Horten was 27 at the time of the Alsberg sale and advertised his purchase in a Nazi party newspaper, saying the store had “passed into Aryan ownership.”

The Aryanization of Jewish businesses in Germany took place in two stages. Before 1938, pressure from the Third Reich led Jews to sell their businesses, at times at deep discounts. After 1938, the sales were typically forced, and the prices paid often sank even lower. Horten was active during both phases, according to historians, who said he was involved in deals that spanned the Nazi takeover of Europe from Amsterdam to East Prussia.

Last year, a historian hired by Heidi Horten to investigate the nature of her husband’s fortune released a lengthy report that said Helmut Horten had clearly benefited from the acquisition of Jewish businesses sold under duress, but that the level of wealth he realized from those activities had been exaggerated.

The historian, Peter Hoeres, said in his report that while Horten had exploited his opportunities, he had initially paid “quite normal market prices” for the Jewish companies, had been “comparatively fair” in relation to the deals struck by other German businessmen and had to navigate his own complex relationship with the Nazis.

The study concluded that Horten’s actions were governed by an opportunistic business sense rather than Nazi ideology, and it cited several instances in which Horten kept on some Jews as either employees or suppliers, in contrast to the government’s efforts. It also noted that, although Horten was a Nazi party member, he was later expelled.

Critics of the report have said it downplayed the extent to which Horten benefited from Aryanization.

“As a historian, I could not agree with the main narratives in the Hoeres report,” said Birgit Kirchmayr, a member and senior adviser of the Austrian Art Restitution Advisory Board, explaining that it was not enough to just say that Horten “was not worse than others.”

Hoeres has defended his study as balanced, though in an interview he said he regretted using the phrase “comparatively fair,” which he said had led some to mistakenly conclude he was minimizing the impact Horten had on Jewish business owners. He noted that his report had surfaced information that Horten used forced labor at a Berlin company he purchased in 1943 that repaired airplanes. “We have done research in 27 archives in Europe and have read thousands of articles and talked to a lot of contemporary witnesses,” he said in an email, calling the results a “good job.”

“We have tried to get the facts and we have not tried to whitewash it,” Hoeres said. “What you have is a mixed picture of Horten.”

Among those who have taken issue with the report is Stephanie Stephan, a journalist in Munich, who released a book last year detailing Horten’s acquisition of Jewish businesses. She said the subject had been quite personal to her because her father, Reinhold Stephan, had been on the board of one of the companies, Gerzon, a fashion house with headquarters in Amsterdam. She said the Jewish owners were forced to sell to Horten, and she published an affidavit from one of them, Arthur Marx, who said Horten had threatened them with being deported to concentration camps if they resisted his takeover.

“My father rebelled against Horten from the very beginning because he knew that he had already forced several Jewish owners of department stores in Germany to sell their department stores for ridiculous sums,” Stephan said. “He immediately dismissed my father. Horten made sure that my father was imprisoned several times and finally was expelled from the Netherlands.”

Hoeres said in an interview that in an upcoming book he will cite research that demonstrates Horten never finalized the purchase of Gerzon, and he disputed the accuracy of Marx’s affidavit, saying it was not supported by records from that era.

Heidi Horten was 19 when she met her future husband, who was more than three decades older. They married in 1966, and when Helmut Horten died in 1987, she inherited nearly a billion dollars.

Her husband’s conduct during the war surfaced as a topic of discussion in recent years as she worked to open a museum for her art collection in Vienna that is operated by the Heidi Horten Foundation. The foundation did not respond to questions.

The historian’s review was commissioned then to address the questions that were raised.

Now those questions have surfaced again as Christie’s prepares for the sale. Kirchmayr, the member of the Austrian restitution panel, noted that the auction coincides with the 25th anniversary of the Washington Principles on Nazi-Confiscated Art, a treaty now used around the world to “expeditiously” promote “just and fair solutions” to restitution claims. (Christie’s organized a discussion in Paris marking the occasion earlier this year.)

Kirchmayr said she would have liked to have seen more transparency in the marketing materials Christie’s put forward to promote the Horten sale. None of it initially mentioned Helmut Horten’s dealings with Jewish business owners.

“You can say that the jewelry itself is not looted,” Kirchmayr acknowledged. “But the money is connected with the Nazi past, and this is a fact that has to be mentioned in the biographies of the collectors.”

After some criticism of the sale surfaced, Christie’s added a mention of Horten’s purchase of Jewish businesses that were “sold under duress” and said it would donate a portion of the proceeds from the sale to Holocaust research and education.

“It was never Christie’s intention to hide information about the well-documented history of Mr. Horten,” Guillaume Cerutti, the chief executive at Christie’s, said in a statement.

Robin Pogrebin and Graham Bowley contributed reporting.