Glyphs

Silver necklace with Scorpio glyph made by C. Lago. Picture is courtesy of "ametistagirl" from Flickr 

Glyphs (Internationally known hieroglyphics / symbols used in Western astrology to represent the 12 signs of the Zodiac) are a surprisingly late astrological development- they were used for the first time only circa 10th century C.E.:

Aries: curved horns of the ram or the letter T

Taurus: circle with horns on top

Gemini: like the roman symbol for the 2 (II)

Cancer: like 69 (horizontal)

Leo: small circle connected to lion’s tail

Virgo: looks like the letter M plus the letter V

Libra: pair of scales

Scorpio: looks like the letter M with an erect tail

Sagittarius: looks like an arrow aiming upward

Capricorn: curved tail of a fish or first two letters in the Greek word tragos, which means "goat."

(Source: The Alpha and the Omega by Jim A. Cornwell)

Aquarius: two zigzags one above the other - looks like water

Pisces: back-to-back half circles connected by an horizontal line in the middle