Category: Gem Notes

Phosphophyllite

The mineral is rare and, because of the value of well-formed specimens combined with a low hardness, brittleness, and cleavage, seldom seen faceted.

Sphalerite

Though its best-known source was the Aliva Mine in Spain, the mineral has been sourced in a handful of other places. But it isn’t often seen in jewelry due to a few specific characteristics.

Anglesite

While the mineral might be well known among collectors, its extreme rarity means few in the public or even gem and jewelry trade know about it.

Montana Sapphire

The latest Gem Note dives into the differences in sapphires sourced in Montana and why it’s so hard to price Rock Creek and Missouri River corundum.

Quartz

This issue, the tables turn to look at a mineral family prevalent in the industry—it’s available in a wide range of colors and from a wide range of localities.

Cassiterite

It’s a common mineral, found on every continent, but faceting rough is rare—unfortunate, since its lighter versions can display dispersion almost twice that of diamond.

Pezzottaite

Named after Dr. Federico Pezzotta from the Natural History Museum of Milan for his work on Madagascar’s granitic pegmatites, this rare mineral species is relatively new.

Hauyne

There has never been commercial production of this rare member of the sodalite group, celebrated for its striking blue color.