- Chemical Formula: (Y, Ce, U, Fe)3(Nb, Ta, Ti)5O16,
Yttrium Cerium Uranium Iron Niobium Tantalum Titanium Oxide.
- Class: Oxides
- Uses: A minor ore of rare earth elements and uranium, sometimes
cut as a gemstone
and as mineral specimens.
Samarskite, whose exact name is samarskite-(Y) (the Y is for the yttrium),
is one of several Rare
Earth Oxides. These rare earth oxides form from the leftover elements
that other minerals seem to not want. Other rare earth oxides such as
have very similar properties to samarskite and are often associated with
each other, compounding the problem. Even the common oxide,
is almost indistinguishable from these rare earth oxides without chemical
tests when rutile is found massive.
Samarskite is found in rare earth rich granite pegmatites, a slow cooling
igneous intrusive rock. Samarskite is associated with
and other rare earth minerals. Samarskite is common enough and locally
abundant enough that it has potential to be a valuable resource for its
rare earth metals. But it is its gemstone
use that is what is odd about this mineral. Samarskite can be cut into
attractive gems and used as cabochons, although since the stones are slightly
radioactive, their use as wearable gemstones should be quite ...well...risky!
As mineral specimens, samarskite can be a nice addition to one's collection.
Good crystals are rare, but prized when found. Although the color is usually
just a velvety black the luster is generally high and striking. Remember,
this is a radioactive mineral and should be stored away from other minerals
that are subject to damage from radioactivity and of course human
exposure should be limited !
- Color is dark pithchy to velvety black to dark brown.
- Luster is vitreous to resinous and fresh surfaces can have a
- Transparency: Crystals are nearly opaque.
- Crystal System is orthorhombic; 2/m 2/m 2/m
- Crystal Habits include stubby prismatic crystals often embedded
in the matrix of the host pegmatite; as well as granular and massive.
- Cleavage is poor in one direction.
- Fracture is conchoidal.
- Hardness is 5 - 6
- Specific Gravity is approximately 4.3 - 5.87 (heavy for non-metallic
minerals). Extreme variation caused by variable composition of component
- Streak is reddish brown.
- Other Characteristics: Radioactive and crystals/specimens are
often coated with a limonite
like earthy coating.
- Associated Minerals include quartz,
- Notable Occurrences include the Ural Mountains of Russia also
found in Iveland, Satersdalen, Norway; Sweden; Divino de Uba, Minas Gerias,
Brazil; Madagascar and Mitchell County, North Carolina, California, Maine,
Colorado and Connecticut, USA.
- Best Field Indicators are luster, fracture, color, streak, radioactivity,
associations, environment and specific gravity.