How did the Star of David’s Two Triangles become the Symbols for the Four Elements?

How did the Star of David’s Two Triangles become the Symbols for the Four Elements?

The Greeks proposed the existence of five basic elements. Of these, four were the physical elements – Fire, Air, Water and Earth – of which the entire world is composed. Alchemists eventually associated four triangular symbols to represent these elements.

– Elemental-Symbols, Catherine Beyey, About.com, Altreligion.about.cm (http://altreligion.about.com/od/westernocculttradition/ig/Elemental-Symbols/)

Triangle Basics of Elemental Symbolism

The Triangle Basics of Four Elements Symbolism

EARTH: A downward-pointing triangle with a horizontal
line through it, a triangle pointing down and with a horizontal line through the middle of it.
WATER: A downward-pointing triangle, a triangle pointing down.
AIR: An upward-pointing triangle with a horizontal line through it, A triangle pointing up and with a horizontal line through the middle of it,
FIRE: An upward-pointing triangle,.a triangle pointing up.