The phrase "an assortment of material" is correct and usable in written English.
It can be used when referring to a variety of different items or types of content that are grouped together.
Example: "The artist presented an assortment of material, including paintings, sculptures, and mixed media works."
Alternatives: "a variety of materials" or "a collection of materials."
They grew large; their images increased in number, augmented by fields of abstract patterning, and with an assortment of materials and objects — newsprint, dishcloths, umbrellas — attached to the cloth surfaces.
"Many of them feel that they can dedicate 20 minutes a night to yoga, and they would also like an assortment of materials to assist them, so we are looking into audio, visual and print aids," she said.
Most of the images have mostly been plucked from "The Shining," but Mr. Ascher also draws on other Kubrick titles, including "2001: A Space Odyssey" and "Barry Lyndon," along with an assortment of archival material.
In drawing upon an assortment of source material including diaries (like Andy Warhol's and Ronald Reagan's), biographies, interviews and obituaries, Mr. Brown constructs portraits that have all the immediacy of reportage, all the fanciful detail of fiction.
The storage compartments of the car are never without an assortment of drawing materials and sketch books.
Some of the artists take a more impressionistic approach to celestial phenomena, evoking distant planets and stars using an assortment of everyday materials.
Batting practice #WorldSeries #GameOne @LengelDavid pic.twitter.com/SAY6Mf7aia October 23, 2013 12.26am BST Pregame reading The Guardian has put together an assortment of World Series material for you to browse as we get set for the 2013 World Series.
Now comes an assortment of new synthetic materials, coupled with a special variety of superpressure balloon which, in combination, is poised to yield a solution for our enhanced duration/payload quest.
You will need several different types of stools and chairs in an assortment of colors and materials.
