I've been zincing a lot since last week's PEOTS about Smithsonite or zinc spar. Sphalerite (Zn, Fe)S or zinc sulphide follows next in the zinc mineral series, alphabetically, chemically, and in "sparkliness" or fire. In fact, the red-orange gemmy quality Sphalerite, known to miners as "Ruby Jack," has a dispersion index three times that of diamond:
Sphalerite comes from a Greek word meaning deceptive or treacherous. When the iron content of Sphalerite is high, it is quite black in color (referred to as "Black-Jack" by miners) causing confusion with Galena or lead ore. Both minerals have similar crystal form; the crystal structure of Sphalerite is akin to Diamond.
And, in thin section:
Have you see sphalerite? There are some cool specimens in Franklin, New Jersey, and in the tri-state district of Missouri, Kansas, and Oklahoma.
Blend(e)ing right in,
Dispersion of most common gems showing sphalerite (red) significantly higher than diamond (blue). Anatase has the highest dispersion:
Sunrise (not sunset) over Denver. Note the Broncos Stadium, Pepsi Center, and Coors Field all line up on a northeast /southwest line. Colfax Ave heads east-west for miles and miles. Anyone find City Park east of downtown?
Here is a promo image for the current Denver Art Museum's "Brilliant" exhibit. That lovely yellow gem is likely citrine, a variety of quartz, with a hardness of 7, rather than sphalerite. In the interest of PEOTS research, I may need a trip to the DAM before March, 2015, to confirm.