"sizeable fortune" is correct and can be used in written English.
It refers to a large amount of money or wealth. Example: After years of hard work and wise investments, he had amassed a sizeable fortune that allowed him to retire comfortably at the age of 40.
When he died in 1811 he bequeathed to his son a sizeable fortune, which Kemp expanded to rapturous proportions by marrying a Baring heiress.
Natalie Bancroft, an opera singer whose family agreed to sell Dow Jones and the Wall Street Journal to Murdoch in 2007, made a sizeable fortune of her own from News Corp's $5bn purchase.
The group, which is still largely owned by the family, has created a sizeable fortune for the brothers.The Zuelligs began buying Chinese artworks in the early 1950s through Helen Ling, the American wife of their Singapore associate, who traded Chinese porcelain in Shanghai.
But Ms Deng is still likely to receive a sizeable fortune, and she's also an influential News Corp employee in her own right, playing an important role in the organisation's growth into China, and chief of strategy for MySpace's China operation.
And there's more: She and her husband Marc Andreessen have a sizeable fortune and their own foundation.
But "taking it on the chin" didn't seem to apply to the large-scale property developers making sizeable fortunes as brown-field sites turned into gold mines.
A new wave of successful tech entrepreneurs seem to have more interest in directing their sense of mission - and sizeable fortunes - at addressing social problems than previous generations of corporate philanthropists have had.
But not doing the due diligence on that clearly cost him a second very sizeable personal fortune.
He was, however, born in 1960 in a part of Cornwall that has been inhabited by St Aubyns since the Norman conquest and, as a young man, was in possession of a fortune sizeable enough that he did not have to work (this is almost certainly no longer the case).
While the criminal case is likely to result in a conviction of SAC on at least some charges, a companion civil asset forfeiture action filed the same day gives the government a means to try to take a sizeable chunk of his fortune if the criminal case does not do so.
But before we dump his collected writings into the marina with which he is so often confused, bidding good riddance to once-sacred rubbish and forget about Hemingway altogether, let's remember that Hemingway left a sizeable chunk of his fortune to his many cats and their successive offspring, who still enjoy a life of feline luxury in Florida.
