The sextile belongs to the Hellenistic aspect doctrine codified by Ptolemy, its geometry deriving from the sixfold division of the circle, and its glyph is a six-rayed star or asterisk, the mark following the six equal arcs of the hexagon the aspect inscribes. Unlike the trine and square, the sextile's sign was given a dedicated place in the Unicode Standard rather than being left to a borrowed geometric character: it appears as SEXTILE at U+26B9 in the Miscellaneous Symbols block. The mark is attested together with the rest of the aspect set, conjunction, opposition, square and trine, in the medieval Byzantine codices that preserve Hellenistic Greek horoscopes, and it reached its familiar asterisk-like printed form as astronomical tables and ephemerides were standardised for type in the Renaissance, a later typographic fixing distinct from, and considerably later than, the ancient concept the mark records.
Among the five classical aspects, the sextile shares this purpose-built encoding only with conjunction and opposition; the trine and square instead reuse ordinary geometric shapes drawn from mathematics rather than astrology proper. The choice of a star-like mark rather than the plain hexagon the angle actually inscribes may owe something to the need to distinguish the sign clearly from the six-sided figure itself when both appeared in the same diagram, a practical concern of manuscript and, later, typeset diagram-making rather than a point of astrological doctrine.