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.
This is the Chalk Emerald, a 37.8 carat emerald from Colombia. Colombia is the major source of emeralds. It is nestled in a cluster of 60 pear-shaped diamonds weighing a total of 15 carats. Emerald is a variety of the mineral beryl, which is a silicate of beryllium and aluminum (a cyclosilicate) with the chemical composition Be 3 Al 2 (SiO 3) 6. These specimens are displayed in the Smithsonian Museum of Natural History.