The part of a sentence 'is primarily made of' is correct and usable in written English.
You can use this sentence when you want to indicate that something is composed or constructed mainly from a particular substance or material. For example, "This bridge is primarily made of iron."
Because it is primarily made of stainless steel, it changes color continuously throughout the day as the light changes.
"The building is primarily made of concrete and glass but does have a steel structure for the large spans over the living areas".
Volcanic ash is primarily made of silicates, or glass fibers, which, once ingested into a jet engine, can melt, causing the engine to flame out and stall.
The Helios, which has a top speed of about 25 miles per hour, is so light because it is primarily made of carbon fiber and graphite epoxy composite material, Styrofoam, bulletproof Kevlar fabric and a plastic film covering.
The cartridge (Fig. 1) is primarily made of photosensitive resin, which exhibits good flexibility and adaptive hardness, and its precision reaches up to 0.1 mm.
The zonal circulation is a single wave packet that is primarily made of zonal wavenumber 1 4 with wavenumber 1 having the largest contribution (Wang and Chen 2016).
The F.D.A. said that the labels of some Nestl?uicy Juice products implied they were primarily made of a single juice, like orange or tangerine, rather than a flavored blend of juices.
The objects that the Brooklyn Museum plans to let go are primarily made of ceramic and stone; they include bowls and other vessels, figurines, benches and ceremonialmetates, or grinding stones.
It's primarily made of recycled newspaper and plastic bags, again, from Delhi, India.
While the original metal card was primarily made of a sheet of tungsten, the metallic part was still surrounded by plastic.
Coins were primarily made of gold and silver because they were rare to mine and didn't corrode, thus ensuring a stable weight.
