4.3" Fluorescent Hyalite Opal on Lustrous Black Tourmaline (Schorl)

Schorl, also known as "black tourmaline" or "black schorl", is a black form of tourmaline that often occurs as lustrous prismatic crystals. The crystals can be stubby or elongated and typically feature lengthwise striations. Many schorl crystals have flattened pyramidal terminations. They can also form in radiating, columnar, and stalactitic aggregations, as well as small, needle-like inclusions within quartz (tourmalinated quartz) and in massive form.

Schorl is a basic sodium iron aluminum boro-silicate with the generic chemical formula NaFe2 + 3Al6(BO3)3Si6O18(OH)4 . It has been used for everything from jewelry to piezoelectric guitar pickups.

Hyalite is a transparent to translucent variety of opal that typically bears a globular structure. An amorphous form of silica (SiO2), hyalite opal forms as a volcanic sublimate in volcanic or pegmatic rock and is thereby considered a mineraloid. It can be referred to as water opal, jalite, or even Muller's glass, named after the man who discovered it, Franz-Joseph Müller von Reichenstein. It has a hardness of 5.5–6 on the Mohs scale and exhibits conchoidal fracturing.