Uses
Besides being the chief ore of zinc, sphalerite is also the chief ore of gallium, indium and cadmium. As such, it becomes a way for miners to locate those metals. It can be altered to create hemimorphite, smithsonite and willemite. It has also been used to make a beautiful gemstone in its own right, for collectors only. Though it can resemble a colored diamond, sphalerite is often considered too soft to be set. When it becomes an aggregate with wurtzite and galena, it is called Schalenblende and is polished as an ornamental stone.
Appearance
Sphalerite sometimes is mistaken for galena or siderite. It is distinguishable by various tests. It is considered a lustrous mineral that can produce a sparkle greater than a diamond because of its high refraction index. It has many small faces that can reflect light.
Identification
If you perform a streak test with sphalerite, it will leave a white trail. It can be translucent to completely transparent. If you attempt to crack sphalerite, it will crack evenly in six directions every time. The shattered pieces will all be smooth. It is not magnetic and it can be scratched by a nail.
Location
Sphalerite is a fairly common mineral with large mines in the United States, Mexico, Australia, Italy, Spain, Burma, Peru, Morocco, Germany and England. Not all of the mines produce the same color sphalerite, though. The mineral is usually found in hydrothermal veins. It can be found in all types of rock.
Names
Before being called sphalerite, it was called blende. This comes from a German word meaning "blind" or "deceptive." This is because it resembles galena and would fool miners into mining it for lead that wasn't there. Sphalerite comes from a Greek word meaning treacherous rock; it is treacherous in the sense that is it easily misidentified because of its color. In modern times, the black sphalerite crystal has been nicknamed Black Jack and the red crystal has been nicknamed Ruby Jack.