glauconite
/ˌɡlɔːʊkoʊˈnaɪt, -kɒn-/Definitions
1. noun
A greenish-brown to greenish-blue clay mineral consisting of a mixed-layer silicate of potassium, aluminum, and iron.
“The geologist studied the glauconite deposits to learn about the Earth’s ancient ocean.”
2. noun
A type of sedimentary rock rich in glauconite.
“The glauconite rock formations were visible along the beach after the low tide.”