Quartz is the most common mineral in the earth's crust and as a gem it is also the most commonly used of the minerals. In the form of minute dust particles in the air, it scratches other gemstones of lesser hardness.
Rutilated quartz is transparent rock crystal with golden needles of rutile arrayed in patterns inside. The inclusions are sometimes called Venus hair.
An other mineral inclusion occurs in the variety called tourmalinated quartz, this instead of golden rutile, has black or dark green tourmaline crystals.
This was called in French «flèches d'amour» or Cupid's darts. It has also been called Thetis hairstone, needlestone or sagenitic quartz.