Milarite Gemstone: Properties, Meanings, Value & More

Milarite is a lesser-known part of the beryl group of minerals. As a gemstone, milarite is known for its hexagonal crystals that can be colorless, yellow, or green.

In terms of scarcity, milarite crystals suitable for creating gemstones are quite rare. Most of the minerals in the milarite-osumilite group are rarely faceted.

Our team of experts here at Gem Rock Auctions adore lesser-known gemstones, so we’re excited to share all the properties, history, prices, and fun facts that you need to know about milarite gemstones today.

Pictured above: Colorless milarite crystal from Spain; Image credit: Christian Rewitzer, CC-BY-SA-3.0

About Milarite Stones

Milarite is a rare semi-precious gemstone usually found yellow, green, or colorless. You might mistake milarite for the similar beryl or apatite, both of which are more often found as gemstones.

Beryl shares an essential component of beryllium with milarite, but beryl minerals have a higher hardness of 7.5 to 8 on the Mohs scale. Apatite is a calcium phosphate (much more different composition) with a closer hardness to milarite at 5 on the Mohs scale.

By its name, you might also confuse milarite with millerite. However, millerite is a nickel sulfide with a metallic luster and very low hardness of 3 to 3.5.

When yellow, milarite crystals are beneficial to those born under Gemini. Green milarites are perfect companions for those born under Taurus.

Milarite Specifications & Characteristics

Milarite is a hydrated potassium calcium beryllium aluminosilicate. The formula approved by the International Mineralogical Association (IMA) is KCa2(Be2AlSi12)O30·H2O.

The mineral is in the osumilite group — also called the milarite group or milarite-osumilite group — alongside around 25 other minerals. Other notable group members are sugilite and the famously rare poudretteite.

Most milarite crystals take the shape of hexagonal prisms, though the mineral can also form as intergrowths, grains, or radial-fibrous aggregates.

Milarite properties listed:

• Mohs hardness: 5.5-6

• Color: Colorless, white, gray, light green, yellow-green, yellow

• Crystal structure: Hexagonal

• Luster: Vitreous (glassy)

• Transparency: Transparent to opaque

• Refractive index: 1.529-1.551

• Density: 2.46-2.61

• Cleavage: None

• Fracture: Irregular/uneven or conchoidal

• Streak: White

• Luminescence: Sometimes present; Bluish-white or greenish white fluorescence & phosphorescence under SW-UV, medium whitish green fluorescence & weak phosphorescence under LW-UV

• Pleochroism: None

• Birefringence: 0.003

• Dispersion: Weak to none

Pictured above: Two sugilite cabochons

Types of Milarite-Osumilite Minerals

The milarite-osumilite group has dozens of minerals, from agakhanovite-(Y) to yagiite. We’ll touch on a few of the most relevant ones:

• Laurentthomasite: Rare anhydrous magnesium analogue of milarite with the IMA formula Mg2K(Be2Al)Si12O30; Color is cobalt blue to greenish-yellow with strong pleochroism; Discovered in Madagascar in 2018 & named after French geologist & mineral dealer Laurent Thomas

• Osumilite: Very rare translucent mineral with the IMA formula KFe2Al3(Al2Si10)O30, isostructural with milarite; Color is black, dark blue, brown, pink, or gray with strong pleochroism; Discovered in 1953 in Osumi Peninsula of Japan (hence the name)

• Poudretteite: Extremely rare (among the rarest) gemstone; Has the IMA formula KNa2(B3Si12)O30; Color is colorless or very light pink; Discovered in Canada in 1986 and named after Poudrette family

• Sugilite: Rare mineral with the IMA formula KNa2Fe3+2(Li3Si12)O30; Color is best when vibrant purple and solid (though black or white patterns are common), can also be light yellow, greenish-yellow, brownish-yellow, colorless; Discovered in Japan in 1974 & named after Japanese petrologist Ken-ichi Sugi

Speaking of discoveries, when was milarite discovered?

Milarite History

German mineralogist Gustav Adolph Kenngott wrote the first report on milarite in 1870. Kenngott thought his specimens came from the Val Milà (or Val Milar) valley in Switzerland — hence the name “milarite” — but the specimens were actually from the nearby Giuv Valley (Val Giuv), as corrected by H. Kuschel in 1877.

(Note: In 1954, English mineralogist Robert Luling Parker confirmed a new discovery of milarite in the Val Milar area.)

Despite Kenngott’s early discovery, mineralogists remained in the dark about milarite’s true composition for decades.

Finally, American mineralogist Charles Palache made a breakthrough in 1930 when he wrote about how beryllium was essential to milarite’s composition.

The only milarite crystals known were still all green until 1968, when the first translucent yellow milarite crystals were found in Mexico.

Since then, a few Mexican milarite crystals have been faceted but very rarely. Researchers at the Gemological Institute of America (GIA) reported in 2019 on the first faceted milarite they’d ever studied: a 2.07-carat pale yellow milarite from Brazil.

Pictured above: Photograph of Gustav Adolph Kenngott (1818-1897), discoverer of milarite, by unknown photographer | Image credit: ETH Library, Public domain

Milarite Healing Properties

As a popularly yellow healing crystal, milarite’s meaning reflects the optimistic and hopeful nature of other yellow gemstones.

Physical Healing

In the physical realm, crystal healers recommend milarite for treating issues related to:

• Bladder

• Kidney

• Digestion

• Menopause

• Immune system function

Emotional Healing

On the mental or emotional side, milarite benefits purportedly include:

• Lowering anxiety

• Increasing emotional resilience

• Boosting optimism

• Dispelling negativity

Chakra Healing

Chakra stones are used to open or balance energy centers (chakras) that may be blocked, disrupting the flow of energy throughout your system. Milarite is used as a solar plexus chakra stone, the energy center for identity and character development.

Symptoms of a blocked solar plexus chakra include feeling low self-esteem, detachment, and imposter syndrome. Using stones like milarite to restore balance can invite feelings of purpose, self-assurance, and motivation.

Pictured above: Colorless, transparent milarite crystals with exceptional clarity, form, and luster found in Switzerland | Image credit: Rob Lavinsky, iRocks.com – CC-BY-SA-3.0

Milarite Gemstone Properties

Besides rarity, the factors that influence milarite’s value as a gemstone include color, cut, clarity, and carat weight. As of now, milarite gemstones are not treated and have not been synthesized.

Color

Milarite gemstones range from colorless to green to yellow-green to yellow, sometimes even gray or tan.

The best milarite colors are usually bright yellow, pale yellow, or colorless with few inclusions.

Cut

Given the rarity of facetable material, milarite faceted into any shape is much more valuable than uncut rough. Lapidarists (gem cutters) may opt for freeform shapes, hexagonal shapes to emulate the stone’s natural form, or more traditional faceted cuts like ovals.

Occasionally, milarite may be cut into cabochons. If it’s not faceted, it’s usually sold rough (uncut).

Clarity & Transparency

Clarity describes the degree of visible inclusions, which often lower the transparency and value of a gem. Though milarite can be transparent, it’s often heavily included and semi-translucent, making transparent high-clarity gems a treasure to find.

In the first faceted milarite studied by the GIA, researchers reported needle-like inclusions and a honeycomb of liquid inclusions.

Carat Weight & Size

Transparent, facetable portions of gem-quality milarite crystals are small, so faceted milarite gemstones are also small; anything over 1 carat is large and priced much higher. Well-formed milarite crystals can be 4 cm (~1.6 in) long.

Pictured above: Green milarite crystals perched on white adularia (a variety of orthoclase) and quartz cluster found in Mexico; Brian Kosnar Collection | Image credit: Rob Lavinsky, iRocks.com – CC-BY-SA-3.0

Milarite Formation & Sources

Milarite forms as a primary mineral, meaning it crystallizes from elements carried by groundwater that evaporates as the magma around it cools. The mineral is found in granite pegmatites, alpine fissures or clefts, marble xenoliths, syenites, and low-temperature hydrothermal veins.

Minerals commonly found with milarite include:

• Albite

• Quartz

• Orthoclase

• Fluorite

• Beryl

• Phenakite

• Bertrandite

• Bavenite

• Muscovite

• Microcline

• Celadonite

• Chlorite

• Calcite

• Minasgeraisite-(Y)

Mining Locations

Gem-quality milarite crystals have been found in Mexico, Brazil, and Namibia.

Attractive crystals not suitable for cutting but still great for collecting are known from:

• Switzerland

• China

• Spain

• USA (New Hampshire)

Pictured above: Pale yellow milarite crystals on miniature matrix from Brazil | Image credit: Rob Lavinsky, iRocks.com – CC-BY-SA-3.0

Milarite Price & Value

The price of milarite largely depends on the cut and quality.

Perhaps unsurprisingly, faceted milarite gemstones are the most expensive. Faceted milarites generally range from around $250 to $750 per carat or about $100 to $1,500 total — remember, most of them are under 1 carat, so their price-per-carat is usually higher than their total cost.

Prices for milarite rough are broader, starting around $40 for small, opaque specimens and going up to $280 for large crystal clusters or even over $6,000 for large, translucent milarite crystals.

Milarite Care and Maintenance

Milarite has mid-range hardness, but it’s still best to care for it gently given its rarity. Avoid cleaning milarite with mechanical systems like ultrasonic or steam cleaners.

The best way to clean milarite is with the standard mild soap, warm water, and a soft toothbrush. Dry it with a microfiber cloth and store it separately from other gems.

Frequently Asked Questions

What is milarite?

Milarite is a rare beryllium silicate mineral first discovered in the alpines of Switzerland in 1870. It’s commonly colorless, green, or yellow and lends its name to the milarite-osumilite group of minerals.

What is milarite made of?

Milarite is a hydrated potassium-calcium-aluminum-beryllium silicate with the formula KCa2(Be2AlSi12)O30·H2O, as approved by the IMA. Other mineralogists have written the formula as K2Ca4Be4Al2Si24O60·H2O or K(H2O)Ca2(Be2Al)[Si12O30].

What is the hardness of milarite?

Milarite ranks at 5.5 to 6 on the Mohs hardness scale, similar to minerals like sodalite, augite, chromite, arsenopyrite, and nepheline.

What is milarite an ore of?

Milarite is not used as an industrial ore, though the similar-sounding millerite is a nickel ore. Beryllium — a fundamental part of milarite — does have major uses like medical imaging devices and aerospace technology, but the primary mineral ores are beryl and bertrandite.

What is milarite worth?

It depends on the quality and cut. Faceted milarites go for $250 to $750 per carat while rough milarites range from $40 to over $6,000.

In the Market for Milarite?

Milarite is a lesser-known precious gemstone found in dazzling yellows and greens. Though originally Swiss, Mexican milarites have taken the collector’s world by storm with their beautiful hues, translated wonderfully to a faceted milarite that perfectly rounds out any rare gem collection.

Buy milarite and other rare gemstones today!