Novákite is a rare copper-arsenic mineral typically found as massive or fine-grained aggregates within hydrothermal veins. It is visually similar to other copper arsenides and is usually identified through laboratory analysis or its occurrence in specific historical mining districts in the Czech Republic.

Hardness

3-3.5

Mohs

Luster

Metallic

Streak

Black

Transparency

Opaque

mineralrare

Novákite

Hardness: 3-3.5
Luster: Metallic
Streak: Black
Transparency: Opaque

Is this novákite?

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 novákite with a known reference. Novákite sits at Mohs 3-3.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: black.
3
Read the luster
Hold the specimen under a strong light. Luster: metallic.
4
Match the color range
Compare against the expected color range: steel gray, black.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: aggregates, botryoidal, tarnishes.

Often confused with

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

How to tell apart: Streak differs, so Novákite leaves black, Algodonite leaves white; luster reads metallic on Novákite and bright metallic on Algodonite.

Often found alongside novákite

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

All properties

Chemical formula: (Cu,Ag)₂₁As₁₀
Mohs hardness: 3-3.5
Density: 6.7 g/cm³
Colors: Steel gray Black
Streak: Black
Luster: Metallic
Transparency: Opaque
Crystal system: Monoclinic
Crystal habit: Aggregates, botryoidal, tarnishes
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: In hydrothermal carbonate veins up to 20 cm thick, cutting diopside hornfels lenses in pyroxene gneiss and less commonly in mica schist (Černý Důl mine, Czech Republic)

Where rockhounds find novákite

Classic worldwide localities

Cashin mine, Montrose Co., Colorado, USA
Černý Důl mine, Krkonoše (Giant Mountains), Czech Republic (type locality)

Field-hunting tip

Where it forms: In hydrothermal carbonate veins up to 20 cm thick, cutting diopside hornfels lenses in pyroxene gneiss and less commonly in mica schist (Černý Důl mine, Czech Republic). If you start seeing arsenic, arsenolamprite, koutekite in float, you are in the right ground. Typical habit: aggregates, botryoidal, tarnishes. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify novákite?+

Mohs hardness is 3-3.5. Luster: metallic. The streak is black. Common colors include steel gray, black.

Where is novákite found?+

Notable localities include Cashin mine, Montrose Co., Colorado, USA; Černý Důl mine, Krkonoše (Giant Mountains), Czech Republic (type locality).

Is novákite safe to handle?+

Novákite contains arsenic and copper and calls for real care. Novákite contains arsenic, which is highly toxic if ingested or inhaled as dust. Wash hands thoroughly after handling and avoid grinding or creating mineral dust.

What rocks look like novákite?+

Novákite is most often confused with Domeykite, Algodonite, Koutekite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with novákite?+

Novákite commonly co-occurs with Arsenic, Arsenolamprite, Koutekite, Silver, Löllingite, Chalcocite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does novákite form in?+

What is novákite used for?+

Novákite is used in collector.

Find novákite on the map

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