1) Window patterns 
Frostwork is a type of speleothem (cave formation) composed of acicular (`needle-like`) growths almost always composed of aragonite (a polymorph of calcite) or calcite replaced by aragonite. It is a variety of anthodite. In some caves frostwork may grow on top of cave popcorn or boxwork. ==Formation== The origin of frostwork is somewhat controve.....
delicate figures and patterns in which frost forms on surfaces
• (n.) The figurework, often fantastic and delicate, which moisture sometimes forms in freezing, as upon a window pane or a flagstone.
Frost`work' noun The figurework, often fantastic and delicate, which moisture sometimes forms in freezing, as upon a window pane or a flagstone. 
the delicate tracery formed by frost, esp. on glass. · similar ornamentation, as on metal.