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.
A page from the Causes of Color exhibit... Green emerald. The mineral is transparent emerald, the green variety of beryl on calcite matrix. 2.5 x 2.5 cm. Coscuez, BoyacÃ¡, Colombia. Emeralds are the green, gem variety of the mineral beryl (Beryllium aluminum silicate).