Star ruby is an extremely rare and valuable red gem found in clusters of rubies, which are themselves only found in clusters of bauxite.
In real life
The "star" pattern that this mineral is known for is caused by rutile (Titanium dioxide: TiO2) crystals that have impregnated the host corundum crystal. Star rubies are only smoothed into cabochons, as cutting them with facets does not allow the star pattern to be seen.
[TILE:15][IS_GEM:star ruby:star rubies:OVERWRITE_SOLID][DISPLAY_COLOR:4:7:1][MATERIAL_VALUE:60]
[SOLID_DENSITY:4005] Common to corundums. Range 3960 - 4050