The phrase "formed first" is correct and usable in written English.
You can use it when you want to emphasize that something happened first or before something else. For example, "The Constitution was formed first, followed by the Declaration of Independence."
For one thing, it probably formed first, before the other planets.
Three-quarters of the gold crystallized within rock cracks, he said, suggesting that the rocks formed first.
In any blood vessel the endothelial tube is formed first, and the muscular and elastic layers are added later.
Both sides say they support all three, but Hamas argues that the new government should be formed first, and lead the elections process, while Fatah wants elections first.
Administratively it formed first a sénéchaussée, dependent on Languedoc (capital Villefranche), and later it was attached to the military governments of Guyenne and Gascony.
This is an indication that globular clusters, and thus Population II objects, formed first in the Galaxy and that Population I stars have been forming since.
The Danube vilayet was formed first, in 1864, followed by those of Janina (Ioannina) and Salonika (Thessaloníki, in Greece) in 1867.
Steve started the motor, zoomed toward the newly formed first set of rapids, and told us to grip the rope that rings the top of the raft and to lean forward.
During the Cenozoic, however, the polar lands became cooler and permanent land ice formed, first in the Alaskan mountain ranges and subsequently, by the end of the Pliocene (2.6 million years ago), in Greenland.
In this method a tertiary alcohol reacts with hydrogen cyanide (HCN) in the presence of a concentrated strong acid; a formamide, RNH−CHO, is formed first, which then undergoes hydrolysis.
It indicates that hexagonal CuS is formed first.
