Aquamarine is  part of the Beryl crystal family, along with Emerald and Morganite ( pink colour, a really lovely delicate pink ); a prized gemstone for a very long time, the ancient Romans particularly appreciated the sea-blue of Aquamarine, hence its name “sea water”, or more  literally “water sea”.  Colour ranges from quite pale through to about the strength exhibited in this pair of earrings.
Aquamarine is a semi-precious gemstone, but international demand and relative rareness makes it one of the more costly semi-precious.