Source: Al-Ahram
From pre-dynastic times, early Egyptians made their way to the Sinai Peninsula over land or across the Red Sea in search of minerals. Their chief targets were turquoise and copper, which they mined and extracted in the Sinai mountains.
Archaeologists examining evidence left 8,000 years ago have concluded that some of the very earliest known settlers in Sinai were miners. In about 3,500 BC these mineral hunters discovered the great turquoise veins of Serabit Al-Khadim. Some 500 years later the Egyptians had mastered Sinai and set up a large and systematic mining operation at Serabit Al-Khadim, where they carved out great quantities of turquoise. They carried their loads down the Wadi Matalla to the garrison port at Al-Markha, south of the present village of Abu Zenima, where they set about loading them on board boats bound for the mainland.
The turquoise was so valued that it became an important part of ritual symbolism in ancient Egyptian religious ceremonies. They used it to carve sacred scarabs and fabricate jewellery, or ground it into pigments for painting statuettes, bricks, reliefs and walls.
To mine the turquoise, the Egyptians would hollow out large galleries in the mountains, carving at the entrance to each a representation of the reigning Pharaoh who was the symbol of the authority of the Egyptian state over the mines.
http://weekly.ahram.org.eg/2009/936/he1.htmphotos at the link