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Microlite Gemstones: Properties, Meanings, Value & More

微晶石寶石：特性、含義、價值等

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Microlite is a group of minerals sometimes used as gemstones. They’re generally light yellow, brown, green, or red and small.

Is microlite rare? These minerals come from many places, but large crystals are rare. Faceted microlites are even rarer.

What are facts about microlite? That’s what we’ll be discussing today as cover the types of microlite gemstones, microlite properties, history, prices, and more!

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

What is Microlite?

Some stones in the microlite group are used as semi-precious gemstones. Other terms for microlite include:

• Haddamite

• Metasimpsonite

• Neotantalite

• Niobtantalpyrochlor

• Tantalo-niobate

• Tantapyrochlor

Now, what is the difference between crystallites and microlites? A crystallite is any crystal that’s so tiny, even microscopic, that it isn’t fully crystallized. So a microlite crystal could also be a crystallite.

However, the definition of “microlite” in geology is more similar to crystallite. What is a microlite in geology? It’s any microscopic crystal(s) suspended in an amorphous (non-crystalline), glassy matrix. The matrix is called “microlitic,” and the crystals form when lava rapidly cools.

Back to the mineral group, what are the uses of microlites?

Microlite Uses

One important industrial use of microlites is as a tantalum ore. Tantalum is used worldwide, particularly in electronics and aerospace technology.

Some microlites have important metals like uranium or rare-earth elements (REEs) like yttrium. According to the U.S. Geological Survey in 1960, the maximum content of rare-earth oxides in microlites is 18.4 percent.

Microlites found in the Harding pegmatite in New Mexico, USA, have various uranium content (0.1 to 10 percent by weight percentage), allowing scientists to analyze the effect of alpha-recoil damage on how the minerals transition from crystalline to metamict (non-crystalline).

Pyrochlores and pyrochlore compounds are being studied as potential sources for environment protection catalysis and clean energy.

As a side note, many products have the name “microlite” but aren’t related to microlite minerals, such as:

• Microlite® fiberglass insulation

• Micro-Lite camping trailers

• Microlite contraceptive pills

• MicroLite vermiculite

• MicroLite Plus radiation protective eyewear

Pictured above: Microlite and muscovite crystal specimen | Image credit: Rob Lavinsky, iRocks.com – CC-BY-SA-3.0

Microlite Specifications & Characteristics

Before scientists classified microlite as a group, microlite was considered an individual mineral composed of sodium calcium tantalum oxide with some fluorine.

Now, the formula accepted by the International Mineralogical Association (IMA) for microlites is (Ca,Na)2Ta2(O,OH,F)7. Another possible microlite formula is (Na,Ca)2Ta2O6(O,OH,F).

Microlite minerals are defined as pyrochlores with a predominant tantalum element over niobium and titanium. The larger pyrochlore group consists of cubic oxides with complex chemistry.

The crystal habit of microlites can be octahedral crystals, grains, or masses.

Like many pyrochlore minerals, some microlites have uranium impurities, which can slowly make them metamict, meaning they lose their crystalline structure and become amorphous due to radiation.

Microlite mineral properties listed:

• Mohs hardness: 5-5.5

• Color: Pale yellow, brown, reddish-brown, hyacinth-red, greenish-yellow, green, colorless; May be color-zoned

• Crystal structure: Isometric/cubic

• Luster: Vitreous, resinous, adamantine, waxy, greasy

• Transparency: Translucent to opaque; May be transparent in thin fragments

• Refractive index: 1.98-2.20; 1.93-1.94 if slightly metamict

• Density: 4.2-6.4; Up to 8.34 with impurities or inclusions

• Cleavage: Indistinct/poor on {111}

• Fracture: Subconchoidal, conchoidal, splintery, or uneven/irregular

• Streak: Pale yellow, brown, grayish-white, white

• Luminescence: None

• Pleochroism: None

• Birefringence: None; May show anomalous birefringence when metamict

• Dispersion: None

Pictured above: Fluornatromicrolite on cleavelandite | image credit: Rob Lavinsky, iRocks.com – CC-BY-SA-3.0

Types of Microlite

There are 14 microlite minerals:

Fluorcalciomicrolite

Appearance: Colorless; Adamantine or resinous luster

Formula: (Ca,Na)2(Ta,Nb)2O6F

Varieties: Titan-uranoan fluorcalciomicrolite (formerly tantalbetafite)

Fluornatromicrolite

Appearance: Green or orange; Adamantine luster

Formula: (Na1.5Bi0.5)Ta2O6F

Synonyms: Bismutomicrolite

Hydrokenomicrolite

Appearance: Pinkish-brown; Adamantine or resinous luster

Formula: (◻,H2O)2Ta2(O,OH)6(H2O)

Polytypes: Hydrokenomicrolite-3C and Hydrokenomicrolite-3R

Synonyms: Bariomicrolite

Hydromicrolite

Notes: Possible new species, no published analysis yet

Formula: (H2O,◻)2Ta2(O,OH)6(H2O)

Hydroxycalciomicrolite

Appearance: Yellow, brownish, greenish; Vitreous or resinous luster

Formula: Ca1.5Ta2O6(OH)

Hydroxykenomicrolite

Appearance: Grayish, colorless, yellow-orange, black

Formula: (◻,Na,Sb3+)2Ta2O6(OH)

Hydroxynatromicrolite

Appearance: Blue; Waxy luster

Formula: (Na,Bi3+,◻)2Ta2O6(OH)

Kenoplumbomicrolite

Appearance: Yellowish-brown; Greasy luster

Formula: (Pb,◻)2Ta2O6(◻,OH,O)

Oxybismutomicrolite

Appearance: Black; Resinous luster

Formula: (Bi1.33◻0.67)Σ2Ta2O6O

Oxycalciomicrolite

Appearance: Brownish-yellow to brownish-red; Vitreous or resinous luster

Formula: Ca2Ta2O6O

Oxystannomicrolite

Appearance: Yellowish-brown; Reddish-brown internal reflections

Formula: Sn2Ta2O6O

Oxystibiomicrolite

Appearance: Greenish-white to white; Gray in reflected light

Formula: (Sb3+,Ca)2Ta2O6O

Uranmicrolite

Appearance: Yellowish-brown, greenish-brown, brownish-black, or yellow; Waxy or greasy luster

Formula: (Ca,U,Na)2-x(Ta,Nb)2(O,OH)7

Synonyms: Djalmaite

Yttromicrolite

Appearance: Black to dark brown; Vitreous luster

Formula: (Ca,Y3+,U,Na)2-x(Ta,Nb,Ti,Fe3+)2O7

Synonyms: Hjelmite, Yttrian oxycalciomicrolite

Notes: Often metamict

Image credit: Mmmmkobayashi, CC-BY-SA-3.0

Microlite History

American mineralogist Charles Upham Shepard made the first recorded discovery of microlite in 1835 based on specimens in Massachusetts, USA. He chose the name after the Greek term mikros, meaning “small,” because the crystals were tiny.

The IMA revised the definition from mineral to mineral group in 2010.

Discovery of Each Microlite Mineral

We’ve listed each microlite’s discovery:

1. 1860 – Yttromicrolite: First specimens from Sweden named hjelmite by Nordenskiöld in 1860, redefined as yttromicrolite by Crook in 1979

2. 1939 – Uranmicrolite: First specimens from Brazil described in 1939 and named djalmaite by Guimarães, redefined as uranmicrolite by Hogarth in 1977

3. 1967 – Oxystannomicrolite: First specimens from Sukula pegmatites in Finland named sukulaite in 1967 by Vorma & Silvola, renamed by stannomicrolite Hogarth in 1977, renamed oxystannomicrolite by Atencio et al in 2010

4. 1981 – Hydroxykenomicrolite: First specimens from Russia named cesstibtantite by Voloshin in 1981, renamed hydroxykenomicrolite by Atencio et al in 2010

5. 1982 – Kenoplumbomicrolite: First specimens from USSR named plumbomicrolite by Stepanov et al, renamed kenoplumbomicrolite by Atencio et al in 2010

6. 1983 – Hydroxynatromicrolite: First specimens from China named natrobistantite by Voloshin et al in 1983, redefined (in part) as hydroxykenomicrolite by Atencio et al in 2010

7. 1986 – Hydrokenomicrolite: First specimens from Brazil named parabariomicrolite by Ercit et al in 1986, divided and redefined into subtypes hydrokenomicrolite-3R and hydrokenomicrolite-3C by Andrade et al in 2013

8. 1987 – Oxystibiomicrolite: First specimens from Sweden named stibiomicrolite by Groat et al in 1987, renamed oxystibiomicrolite by Atencio et al in 2010

9. 1998 – Fluornatromicrolite: First specimens from Brazil named fluornatromicrolite by the IMA in 1998

10. 2004 – Oxycalciomicrolite: First specimens from Sweden named stibiomicrolite by Černý et al in 2004, redefined as oxycalciomicrolite by Christy & Atencio in 2013

11. 2010 – Hydromicrolite: Described as possible new species by Atencio et al in 2010; Only currently known locale is Poland

12. 2012 – Fluorcalciomicrolite: First specimens from Brazil named fluorcalciomicrolite by Andrade et al in 2012

13. 2013 – Hydroxycalciomicrolite: First specimens from Brazil named hydroxycalciomicrolite by Andrade et al in 2017

14. 2019 – Oxybismutomicrolite: First specimens from Russia named oxybismutomicrolite by Kasatkin et al in 2019

Pictured above: Albite specimen with a sprinkle of transparent, red-orange microlite crystals | Image credit: Rob Lavinsky, iRocks.com – CC-BY-SA-3.0

Microlite Healing Properties

Microlite’s meaning as a healing stone can depend on its color. Yellow microlite joins yellow gems in symbolizing warmth, while green microlites have the renewing properties of other green gems. Meanwhile, brown microlites join other brown gemstones in being chakra stones for the root chakra.

Microlite Gemstone Properties

Besides rarity, microlite gemstone value depends on its color, cut, clarity, transparency, and carat weight.

Color

Most microlites are pale yellow, brown, or colorless, but vibrant colors like emerald green and orange-red are valuable.

Cut

Facetable rough is rare, making faceted microlites exceptionally valuable.

Massive material can become cabochons or carvings.

Clarity & Transparency

Microlite gems with few to no visible inclusions are quite rare and valuable.

Often, microlite is an inclusion in stones like topaz or aquamarine.

Carat Weight

Most faceted microlites are under 3-4 carats. Green Brazilian microlite gems have the potential for large sizes.

Massive material can be cut into large cabochons.

Pictured above: Transparent golden-orange microlite crystals on yellowish-green muscovite | Image credit: Rob Lavinsky, iRocks.com – CC-BY-SA-3.0

Microlite Formation & Sources

What rock is microlite found in? Microlites are primary minerals in albitized or lithium-bearing granite pegmatites, where they formed from the pegmatite magma.

Mining Locations

Where is microlite found? The top sources for gem-quality microlites are Brazil and Virginia, USA.

Other significant sources include:

• Australia

• Austria

• FInland

• France

• Greenland

• Madagascar

• Norway

• Sweden

• USA (Colorado, Connecticut, Maine, Massachusetts, New Hampshire, South Dakota)

Pictured above: Green microlite crystal and scattered golden-amber microlites on albite specimen | Image credit: Rob Lavinsky, iRocks.com – CC-BY-SA-3.0

Microlite Price & Value

Given their rarity, faceted microlite gems can be pricey, ranging from around $285 to nearly $1,100 per carat.

Microlite rough also ranges broadly, from $65 to $1,200. Rough that’s on a matrix with other minerals ranges from $60 (topaz matrix) to $3,000 (tantalite matrix).

Microlite Care and Maintenance

Before we discuss gemstone care, it’s important to note that some microlites can be slightly radioactive from rare-earth element impurities.

Stones that are already cut or polished should be fine to handle, but take safety precautions if you’re cutting or handling rough microlites so you don’t inhale any of the resulting dust that can fly off.

To keep your microlite safe, opt for jewelry with protective settings and keep it stored away from harder gems.

Clean microlite stones with a soft toothbrush, warm water, and mild soap.

Make the Most with Microlite!

Sometimes the smallest treasures are the best. Plus, microlite’s rarity makes it a staple in any collection!

Buy microlite and other magnificent gemstones today!