Star garnet is about as rare as cabochon material gets, found in gem quality in only two places on the entire planet, Idaho and India.
What you're looking at is deep red to reddish black garnet with tiny rutile needles trapped inside, aligned in a way that reflects light into a genuine four or six pointed star effect when the stone catches direct light at the right angle.
That effect, called asterism, is why this material can never be faceted the way most gems are, cutting it any other way than as a cabochon would destroy the very structure that creates the star.
It's part of the same garnet family that serves as the January birthstone, so beyond its rarity, it carries that personal, gift worthy meaning too.
A direct light source, a flashlight, sunlight, or even a phone light, brings the star out clearly against the stone's dark, rich body color.