The phrase "amassed a vast collection" is correct and usable in written English.
You can use it when describing the act of gathering or accumulating a large number of items, typically in a specific category or subject.
Example: "Over the years, she amassed a vast collection of rare stamps from around the world."
Alternatives: "built an extensive collection" or "gathered a large assortment".
This family memoir chronicles the life of the author's grandfather, who amassed a vast collection of Soviet literature and Judaica.
He also amassed a vast collection of bird specimens, many later donated to the natural history museum.
Decades after his first acquisition, Mr. Hammett, 50, has amassed a vast collection that includes horror movie posters, toys, dolls, games, costumes, masks, original artwork and other mementos.
His most recent crusade is particularly striking because of the beneficiary: a man who has amassed a vast collection of child pornography.
He has devoted years to studying the style, amassed a vast collection of period furniture and started a business renovating prewar apartments for expatriates.
Hackers amassed a vast collection of security clearance records, even fingerprints, in a yearlong hacking of the United States Office of Personnel Management.
Charles H. McCaghy, a professor emeritus of sociology at Bowling Green State University in Ohio who amassed a vast burlesque collection dating to the 1870s, said that he was amazed at the comeback.
He also amassed a vast, important collection of his own: besides paintings and drawings it included textiles, arms and armor and stone carvings.
Mr. Falk, who died in 1992 at 85, began amassing a vast collection of Asian art after making a trip to China in 1936.
Behind the front gate, the owner seemed to be amassing a vast collection of rusty shopping carts and cardboard boxes, a landscaping style that borrowed more from "Hoarders" than HGTV.
Uli Sigg, the Swiss Ambassador to Beijing, who was amassing a vast collection of contemporary Chinese art, became an avid booster and introduced him to, among others, Harald Szeemann, the curator of the 1999 Venice Biennale.
