The phrase "are primarily composed" is correct and usable in written English.
It can be used when describing the main components or elements that make up something.
Example: "The committee members are primarily composed of experts in environmental science."
Alternatives: "are mainly made up" or "are chiefly formed".
Tanzania's native forests are primarily composed of hardwoods, but softwood production is increasing.
Bulk mineralogical analyses with infrared (IR) spectroscopy confirm that all samples are primarily composed of CaOx (see Methods).
The pore types are primarily composed of elliptical and irregular intergranular pores.
Speleothems are primarily composed of calcium carbonate, precipitated from groundwater that has percolated through the adjacent carbonate host rock.
Proanthocyanidins (PAs) are primarily composed of the flavan-3-ol subunits -epicatechin and/or -catechin, but the basis for their different starter and extension unit compositions remains unclear.
The idea behind the beat-detection algorithm is based upon the premise that the strong 'beats' of any sample of music are primarily composed of low frequency components.
The side chains are primarily composed of terminal arabinose and xylose connected to the main chain by O-3 and/ or O-2 linkage.
The proposed switches are primarily composed of piezoelectric cantilever actuators, a contact electrode and coplanar wave transmission lines suspended over the substrate.
Bio-based natural macromolecules are primarily composed of complex polysaccharides that strengthen microbial growth for the production of industrially relevant enzymes.
Cotton fibers are specialized trichomes that are primarily composed of cellulose but have a cuticle composed of free waxes and cutin.
The laterite clays (also known as ion-absorption clays) are primarily composed of silica, alumina, and ferric oxide; those that also contain viable amounts of rare earths are found only in Jiangxi province of southeast China.
