Mineral Of The Day

Mineral Of The Day #163: Stibnite (Revisited)

Mohs Hardness Scale: 2
Category: Sulfide mineral
Formula:
Sb₂S₃

Fun Facts:

• Historically, pastes of stibnite and fat materials have been used since 3000 BC as eye cosmetics called kohl in the Middle East.
• Stibnite is most commonly pulverized and heated to extract the antimony and make flame retardants and engine bearings.
• It is also used in making fireworks (Happy Fourth of July!).

Mineral Of The Day #144: Covellite

Mohs Hardness Scale: 1.5-2
Category: sulfide mineral
Formula: CuS

Fun Facts:

• Covellite was named after Niccolo Covelli (1790-1829), an Italian mineralogist and discoverer of the mineral at Mount Vesuvius.
• It is usually an indigo-blue and massive metallic mineral.
• Although good crystals are rare, covellite’s luster and color make it noteworthy to mineral collectors.
• Covellite was the first-discovered natural superconductor!
  

Mineral Of The Day #131: Pyrrhotite

Mohs Hardness Scale: 3.5-4.5
Category: sulfide mineral
Formula: Fe_1-xS (x = 0 to 0.2)

Fun Facts:

• Pyrrhotite gets its name from the Greek pyrrhos, meaning “flame-colored.”
• Pyrrhotite has varying magnetic powers, depending on the number of Fe vacancies in its crystal structure.
• A related species with no vacancies (and therefore non-magnetic) is called “troilite” and has been found in meteorites!

Mineral Of The Day #126: Realgar

Mohs Hardness Scale: 1.5-2
Category: sulfide mineral
Formula: As₄S₄ or AsS

Fun Facts:

• Realgar gets its name from the Arabic rahj al gar, which means “powder of the mine.”
• It is also known as “ruby sulfur” or “ruby of arsenic.”
• Realgar, along with orpiment and arsenopyrite, provide nearly all of the world’s supply of arsenic.
• It was used by firework manufacturers to create the color white in fireworks!
• Historically, realgar was used as a pigment and a medicine in the Roman Empire.
• Realgar is one of the few sulfides that is not metallic, opaque, or blandly-colored!
• Realgar specimens should be stored in dark, enclosed containers and only exposed to light for brief encounters because they will break down and eventually become a powder over time.

Mineral Of The Day #125: Marcasite

Mohs Hardness Scale: 6-6.5
Category: sulfide mineral
Formula: FeS₂

Fun Facts:

• Marcasite is a polymorph of pyrite (meaning it has the same chemical formula as pyrite, but a different crystal structure).
• The most famous habit for marcasite is the “cock’s comb” twinned habit. The crystals appear like a rooster’s head crest, hence the name.
• It is used as a minor ore of iron, a source of sulfur, and as mineral specimens.
• “Marcasite jewelry” is actually made from pyrite, not marcasite!

Mineral Of The Day #119: Gold

Mohs Hardness Scale: 2.5
Category: Native element

Formula: _Au

Fun Facts:

• Spinning straw into gold for three consecutive nights makes a woman eligible to marry a king.
• There is a pot of it at the end of every rainbow.
• Everything that King Midas touched turned to gold.
• Alchemy is the process by which copper and other base metals are turned to gold by way of an elixir.
• Medically, gold is used in dentistry, and it makes an attractive gold tooth.

APRIL FOOLS!

Mineral Of The Day #119: Pyrite

Mohs Hardness Scale: 6-6.5
Category: Sulfide mineral

Formula: FeS₂

Fun Facts:

• Pyrite is also known as “Fool’s Gold” because of its resemblance to gold.
• It is the most common sulfide mineral.
• It was used in the 16th and 17th centuries as a source of ignition in early firearms.
• Commercially, it is used for the production of sulfur dioxide, which is used in the paper industry.
• Pyrite is also used to make marcasite jewelry.

Mineral Of The Day #111: Millerite

Mohs Hardness Scale: 3-3.5
Category: Sulfide mineral

Formula: NiS

Fun Facts:

• Millerite was named after the English mineralogist, W. H. Miller (1801-1880) who first studied its crystals.
• Millerite is one of a few sulfide minerals that form fine acicular crystals that appear as hair-like fibers aggregated into sprays.
• Millerite usually forms in hydrothermal replacement deposits and in limestone and dolomite cavities and associated geodes.
• It is a real bonus to quartz geode collectors to open up a geode and find a brassy spray of millerite crystals tucked inside!

Mineral Of The Day #81: Enargite

Mohs Hardness Scale: 3
Category: sulfosalt, sulfide mineral
Formula: Cu₃AsS₄

Fun Facts:

• Enargite gets its name from the Greek enarge, which means “distinct” (referring to this mineral’s cleavage).
• Typically dark-grey to black, it is a somewhat rare copper mineral.
• Its crystals that form tabular or prismatic habits are often pseudohexagonal.
• Enargite is used as a minor ore of copper and as mineral specimens!

Mineral Of The Day #76: Chalcopyrite

Mohs Hardness Scale: 3.5
Category: sulfide mineral
Formula: CuFeS₂
Fun Facts:

• Due to its color and its high copper content, chalcopyrite is often referred to as “yellow copper.”
• It is an important copper ore.
• It is sometimes polished into beads and pendants to make cheap jewelry.
• Chalcopyrite can have an iridescent tarnish that makes it resemble bornite (“peacock ore”).

Mineral Of The Day #66: Bornite