Formicaite is an extremely rare calcium formate mineral typically found in environments containing decomposing organic matter and limestone. It usually appears as small, thin, tabular crystals in cavities of sedimentary rocks, often requiring micro-analysis for definitive identification.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Semitransparent

mineralrare

Formicaite

Hardness: 1
Luster: Vitreous
Streak: White
Transparency: Semitransparent

Is this formicaite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch formicaite with a known reference. Formicaite sits at Mohs 1, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: white, light blue.
5
Look at form & habit
Crystal system: tetragonal. Typical habit: aggregates, microscopic crystals, tabular.

Often confused with

Formicaite vs. its common look-alikes, and how to tell them apart in the field.

mineral

Calcite

Mohs 3

How to tell apart: Calcite is the harder of the two (Mohs 3 vs. 1).

How to tell apart: Luster reads vitreous on Formicaite and subvitreous, pearly on {010} cleavages, silky if fibrous on Gypsum.

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Often found alongside formicaite

Minerals reported to co-occur with formicaite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: Ca(HCOO)₂
Mohs hardness: 1
Density: 1.9 g/cm³
Colors: White Light blue
Streak: White
Luster: Vitreous
Transparency: Semitransparent
Crystal system: Tetragonal
Crystal habit: Aggregates, microscopic crystals, tabular
Cleavage: {100}, perfect
Rarity: Rare
Uses: Collector
Host rock: Rare in hydrothermal veinlets cutting kurchatovite-sakhaite ore (Solongo deposit, Russia); in a veinlet in skarnitized marble (Novofrolovskoye deposit, Russia)

Where rockhounds find formicaite

Classic worldwide localities

Solongo boron deposit, Buryatia, and the Novofrolovskoye copper deposit, near Krasnoturinsk, Turinsk district, Northern Ural Mountains, Russia

Field-hunting tip

Where it forms: Rare in hydrothermal veinlets cutting kurchatovite-sakhaite ore (Solongo deposit, Russia); in a veinlet in skarnitized marble (Novofrolovskoye deposit, Russia). If you start seeing calcite, lizardite, frolovite in float, you are in the right ground. Typical habit: aggregates, microscopic crystals, tabular. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify formicaite?+

Mohs hardness is 1. Luster: vitreous. The streak is white. Common colors include white, light blue.

Where is formicaite found?+

Notable localities include Solongo boron deposit, Buryatia, and the Novofrolovskoye copper deposit, near Krasnoturinsk, Turinsk district, Northern Ural Mountains, Russia.

What rocks look like formicaite?+

Formicaite is most often confused with Calcite, Gypsum. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with formicaite?+

Formicaite commonly co-occurs with Calcite, Lizardite, Frolovite, Pentahydroborite, Hexahydroborite, Vimsite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does formicaite form in?+

What is formicaite used for?+

Formicaite is used in collector.

Find formicaite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.