Mineral Of The Day

Mineral Of The Day #155: Rutile

Mohs Hardness Scale: 6-6.5
Category: Oxide mineral
Formula: TiO₂

Fun Facts:

• Named for the Latin rutilus, red, in reference to the deep red color of some specimens when viewed by transmitted light.
• Rutile is used in the manufacture of refractory ceramics and for the production of titanium metal.
• Finely powdered rutile is used a brilliant white pigment!
• Rutile is used in sunscreen to protect against UV induced skin damage.
• Small rutile needles present in gems create an optical phenomenon known as asterism. Asterated gems are known as “star” gems (star sapphires, star rubies, etc.).

Mineral Of The Day #139: Augite

Mohs Hardness Scale: 5-6.5
Category: inosilicate mineral, pyroxene group
Formula: (Ca,Na)(Mg,Fe,Al)(Si,Al)₂O₆

Fun Facts:

• Augite is an important rock-forming mineral. It is found in igneous rocks and high-temperature metamorphic rocks.
• Occasional augite specimens have a shiny appearance that give rise to the mineral’s name, which is from the Greek augites, meaning “brightness.” Ordinary specimens have a dull (dark green, brown, or black) finish.

Mineral Of The Day #120: Hübnerite

Mohs Hardness Scale: 4-4.5
Category: Sulfate mineral

Formula: MnWO₄

Fun Facts:

• Hübnerite occurs in high-temperature hydrothermal veins.
• It was first described in 1865 and named after the German mineralogist, Adolf Huebner.
• It is a manganese-rich variety of the mineral wolframite.
• According to crystal healers, hübnerite can be used to expand one’s creativity and insight.

Mineral Of The Day #107: Franklinite

Mohs Hardness Scale: 5.5-6.5
Category: Oxide mineral, spinel group

Formula: ZnFe₂O₄

Fun Facts:

• Franklinite is one of the minerals found in Franklin, NJ — a world-famous locality that has produced many formerly unknown and exotic mineral species.
• This dark black mineral is only found in Franklin and Ogdensburg in Sussex County, NJ.
• Franklinite is an ore of zinc and manganese.

Happy birthday to MOTD reader, Lily, a resident of Sussex County, NJ! :)

Mineral Of The Day #103: Jet

Mohs Hardness Scale: 2.5-3
Category: mineraloid

Fun Facts:

• Jet is not considered a true mineral, but rather a mineraloid because it has an organic origin. It is derived from decaying wood under extreme pressure.
• It is a variety of lignite.
• The oldest jet jewelry was found in Asturias, Spain, dating from 17,000 BC!
• Jet was a fashionable gemstone during Victorian times. Queen Victoria wore jet mourning jewelry.
• Jet was associated with mourning jewelry because of its somber color and modest appearance.
• Jet was also popular in 1920s America, when flappers would wear long strands of jet beads strung like pearls.

Mineral Of The Day #98: Labradorite

Mohs Hardness Scale: 6-6.5
Category: tectosilicate mineral, feldspar group
Formula: (Ca,Na)(Al,Si)₄O₈, where Ca/(Ca + Na) (% Anorthite) is between 50%–70%

Fun Facts:

• Generally, labradorite is a dull and dark-looking mineral whose charm can easily be overlooked if not viewed from the proper position.
• It produces a colorful play of light called labradorescence. It displays intense colors such as blue, violet, green, yellow, and orange. Labradorescence is truly a one of a kind mineralogical experience best observed in person!
• It was first found in 1770 on the Labrador Peninsula in Canada.
• It is used as a gemstone.

Mineral Of The Day #80: Goethite

Mohs Hardness Scale: 5.-5.5
Category: oxide mineral
Formula: FeO(OH)

Fun Facts:

• Goethite is named after German poet, novelist, playwright, philosopher, and geoscientist Johann Wolfgang von Goethe (1749-1832).
• It is used as an iron ore.
• It is a brown ochre clay earth pigment. Clay earth pigments dry fast in oil painting and are relatively inexpensive. They have been used since prehistoric times in cave painting!
• Goethite is found all over the world in soil and other low-temperature environments. NASA’s Spirit rover found it on Mars!