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.
On the Mohs scale of hardness Emeralds can range from a 7.5 to an 8. The emerald s green color is caused by the presence of chromium and iron. Emerald is a variety of green beryl whose chemical formula is Al2Be3Si6O18. Most of the world s emeralds are found in Columbia, Brazil, and Zambia.