Hexagonal prisms of aquamarine embedded in a substrate of flaky muscovite, a common micaceous mineral. Aquamarine is a variety of beryl, the blue to blue-green variety, named after the Latin for 'water of the sea'. Minerals of the beryl suite are usually found in pegmatites, complex rock suites formed at great depth. Sample size is 150 mm and is from the Nagar district of Pakistan. With coin for scale.