Millerite Gemstone: Properties, Meanings, Value & More

Millerite is a rare, brassy yellow-colored mineral known for its attractive needle-like crystal habit and heaviness. The gemstone also has a strong metallic luster that shines brightly.

How rare is millerite? Millerite is relatively rare — there are many locations with small amounts of the mineral, but not many substantial deposits. Attractive specimens are sought-out by rare mineral collectors.

In this guide, we’ll break down everything you need to know about millerite, from its properties and powers to its prices and history.

What Is A Millerite Crystal?

Millerite is a semi-precious gemstone, though it’s not often used in jewelry.

Because of its similar appearance to pyrite and the way its capillary habit resembles tufts of hair, millerite is sometimes referred to as “hair pyrite.” You’ll often see these tuft-like crystal clusters inside millerite geodes. Pyrite is a completely different mineral, however.

What does millerite look like? This stone is usually a pale brassy yellow color. Its appearance is similar to pyrite or chalcopyrite, but yellower than both and creamier than chalcopyrite. Millerite also has a slightly iridescent tarnish.

Besides the “hair pyrite” nickname, other synonyms for millerite include:

• Capillary Pyrite

• Nickel Pyrite

• Trichopyrite

• Archise

• Capillose

Astrologically, millerite is a zodiac stone for the fire element signs: Aries, Leo, and Sagittarius. The crystal is also a planetary star stone for the sun and Mercury.

What are the uses of millerite? Industrially, millerite is a minor source of nickel. Synthetic millerites are created for studying nickel extraction.

Image credit: Rob Lavinsky, iRocks.com – CC-BY-SA-3.0

Millerite Specifications & Characteristics

What is millerite made of? The mineral’s composition is nickel sulfide, so the millerite formula is NiS. Common impurities in millerite are iron, cobalt, and copper.

The most similar mineral to millerite is pentlandite. Pentlandite is an iron-nickel sulfide with an isometric (cubic) crystal system, different from millerite’s trigonal system. Both can have a yellowish-bronze color and metallic luster. However, pentlandite has a lower density (4.6 to 5) and slightly higher Mohs hardness (3.5 to 4).

You can differentiate millerite from pentlandite with a streak test, as pentlandite has a light brownish-bronze streak while millerite has a greenish-black streak. However, streak tests are destructive and should only be done on rough as a last resort for identification.

The crystal habits of millerite include capillary (hair-like) or acicular (needle-like) crystals or cleavable masses. The crystals may be fibrous or tufted, and the tufts are often found inside geodes.

You can find all of millerite’s properties listed:

• Mohs hardness: 3-3.5

• Color: Shades of yellow, often brassy or bronze-like; Tarnishes to greenish-gray

• Crystal structure: Hexagonal (trigonal)

• Luster: Metallic

• Transparency: Opaque

• Refractive index: 1.96-2.04

• Density: 5.3-5.6

• Cleavage: Perfect, 2-direction on {1011} and {0112}

• Fracture: Uneven/irregular

• Streak: Greenish-black

• Luminescence: None

• Pleochroism: Present; Weak in air, stronger in oil; Pale yellowish-brown to bright yellow

• Birefringence: None

Millerite Meaning & History

Millerite’s yellow hues reflect its symbolism: enthusiasm, optimism, and prosperity. The brassy to bronze undertones and metallic sheen also represent abundance, ambition, and good luck.

The name “millerite” was chosen by Austrian mineralogist Wilhelm Haidinger in 1845 in honor of Welsh mineralogist Willian Hallowes (W.H.) Miller.

Miller was the first person to study millerite crystals, along with establishing modern crystallography in his 1839 Treatise on Crystallography.

The type locality of millerite is in the Karlovy Vary region of Czechia

Image credit: Rob Lavinsky, iRocks.com – CC-BY-SA-3.0

Millerite Healing Properties

Like any gemstone, millerite can be used as a healing stone. This crystal joins other yellow gemstones in promoting focus, strength, and positivity.

Specimens that have tarnished to greenish-gray offer the balancing and grounding powers of gray gemstones, along with the rejuvenating and energizing properties of green gemstones.

Physical Healing

Physically, millerite crystals are purported to help treat issues related to the heart, lungs, and respiratory system overall. It’s also said to help treat digestive problems.

Emotional Healing

Crystal healers recommend millerite for transforming negative energy into positive energy and balancing your emotions. It may also help you handle stress more effectively and communicate with compassion, facilitating healthier relationships.

Chakra Healing

Energy healing involves opening one or more of the seven chakras (energy centers) along your body to resolve the negative symptoms associated with a chakra being blocked.

Millerite is a chakra stone for the solar plexus chakra, located just below the breast bone. The solar plexus chakra governs identity and growth, so when it’s blocked, you may feel detached, disillusioned, or insecure. Opening it with millerite brings feelings of greater confidence, self-respect, and ambition.

Image credit: Rob Lavinsky, iRocks.com – CC-BY-SA-3.0

Millerite Gemstone Properties

Since millerite is only somewhat common in collections, it doesn’t have established grading criteria. We’ll still touch on how some standard value factors may apply to millerite below:

• Color: Millerite’s color is usually pale brassy yellow, but specimens with rich yellow hues can carry higher value.

• Cut: Millerites found in massive crystal habits can be cut into cabochons, but the stone’s perfect cleavage and softness doesn’t lend well to jewelry use. It is not faceted.

• Luster: Millerite has a bright metallic luster, and specimens with more shine may be more valuable.

• Carat Weight: Massive millerite specimens can be cut into virtually any size for decorative slabs or cabochons.

• Treatments: There are no known treatments for millerite.

Before its cut or sold, millerite has to form, of course. But how does that happen?

Millerite Formation & Sources

Millerite forms through a couple of processes, often in low-temperature conditions. One process involves the metamorphism of pentlandite (or other nickel-rich sulfide minerals) inside serpentinite ultramafic rocks. The metamorphism (or metasomatism) removes pentlandite’s sulfur, so millerite replaces pentlandite in the rock.

The mineral can also form from sulfur and nickel when olivine cumulate rocks that are low in sulfur go through nucleation (a process of crystal growth). Metamorphism pushes out the sulfur and nickel in these rocks, which are reconstructed into millerite and other similar minerals.

Millerite is also sometimes associated with the mineral heazlewoodite, a rare nickel sulfide low in sulfur, and can turn into heazlewoodite with more metamorphism.

Miners usually find millerite in copper-nickel sulfide deposits, but it’s also found in hematite, serpentine, dolomite, and carbonate deposits. Geodes containing millerite often occur in limestone.

Mining Locations

Where is millerite found? The top source for millerite specimens is Lincoln County, Kentucky, USA, specifically the Halls Gap area. There are also millerite tufts inside geodes in Missouri and needle-like crystal sprays in Antwerp, New York. Pennsylvania produces needle-like millerite tufts.

Many millerite masses (used to make cabochons) come from Ontario and Manitoba, Canada.

Besides the ones mentioned, additional millerite sources include:

• Austria

• Czechia

• Germany

• Slovakia

• UK (Wales)

• USA (Illinois, Wisconsin, Iowa, Michigan, Indiana)

Now, how much does millerite cost?

Image credit: Rob Lavinsky, iRocks.com – CC-BY-SA-3.0

Millerite Price & Value

As a rare mineral, millerite can be pricey. But it’s also not in high demand, so some specimens are much more affordable.

Large, attractive millerite crystal specimens like radiating sprays or geodes can cost $1,400 to $3,500. Other crystal specimens can range from $15 to $120 each, depending on the size, quality, source, and seller.

Millerite Care and Maintenance

Lastly, we’ll discuss proper gemstone care for millerite. As mentioned before, millerite is too fragile for jewelry use, though you may be able to wear it occasionally if the jewelry has protective settings.

Since it’s a soft mineral with perfect cleavage, it can be scratched or broken pretty easily. We recommend keeping it away from other minerals and storing it in a fabric pouch or fabric-lined box.

To clean the mineral, simply use a soft toothbrush, warm water, and mild soap.

Make a Splash with Millerite!

Millerite is a lesser-known rare mineral, but its beautiful crystal formations make it a star for decor or collections. Plus, you can say you have a crystal specimen most people have never seen!

Shop for unique gemstones today!