A period is a bleed from the womb (uterus) that is released through the vagina. It happens approximately every 28 days, although anywhere between 24 and 35 days is common. Periods can begin when girls are between 8 and 16 years old, but usually start around the age of 12.
Emerald is a gemstone and a variety of the mineral beryl (Be3Al2(SiO3)6) colored green by trace amounts of chromium and sometimes vanadium. Beryl has a hardness of 7.5â8 on the Mohs scale. Most emeralds are highly included, so their toughness (resistance to breakage) is classified as generally poor.
Emerald Emerald is the most popular green gemstone in the United States and most of the world. Opal Photos Pictures of Opal A collection of different types of opal from all around the world and Mars too! U.S. Gemstones United States Gemstones Small mines in the U.S. produce a diversity of gemstones.