Grapefruit is oblate in shape, ranges in diameter from 3 to 5 inches and can weigh up to 150 g. Characteristically, it has thick, tough skin than that in the oranges. Inside, the fruit is segmented into arils as in other citrus fruits.
Nacre (/ËneÉªkÉr/ NAY-kÉr also /ËnÃ¦krÉ/ NAK-rÉ),[1] also known as mother of pearl, is an organic-inorganic composite material produced by some molluscs as an inner shell layer; it also makes up the outer coating of pearls. It is strong, resilient, and iridescent.
Thus the growth of the shell in extent is due to additions to the prismatic layer at the edge, its growth in thickness to new layers of nacre deposited on its inner surface. Perna and pernocchia meant a shellfish which yielded nacre or mother-of-pearl.