rare metal

Erbium, a rare metal found along with yttrium, terbium, and other rare elements in some rare minerals.

Thallium is a rare metal, found in small quantities in some varieties of iron and copper pyrites, and in some lithia micas.

There were plenty of weapons, a few cassava-making implements, a rare metal dish or tin can and hammocks everywhere.

Terbium, ter′bi-um, n. a rare metal found in certain yttrium minerals.

Radium is a rare metal recently discovered, having remarkable qualities and very difficult to obtain.