Zirdan is large enough to maintain a spherical shape, but has no atmosphere.
With a diameter of .51 times earth, Zirdan's heavier qualities make it have a mass of 0.25 times earth. Its density is due to heavier zinc and copper-based carbonates such as azurite.
Zirdan is mainly heavier carbon compounds such as hydromagnesite, a magnesium-carbon compound. Unlike most zinc-copper planets, Zirdan is more magnesium and sodium-based. Other minerals feature dolomite, lansfordite, and natrite. Zirdan has no atmosphere.