Novákite

Chemical formula: (Cu,Ag)₂₁As₁₀

Novákite is a rare copper and silver arsenide, forming steel-gray, metallic aggregates, discovered in the Czech Republic.

## Characteristics Novákite is a rare mineral from the arsenide group, consisting mainly of copper and silver. It occurs in the form of fine-grained or compact aggregates, rarely forming visible crystals. Its most characteristic feature is its metallic luster and steel-gray color, which on a fresh surface can resemble polished steel. ## Physical Properties This mineral is relatively soft, with a Mohs hardness ranging from 3 to 3.5, which means it can be scratched with a copper wire. It is opaque and has a high, metallic luster. Its density is significant, approximately 6.7 g/cm³, making it heavy in relation to its volume. ## Colors and Varieties Novákite occurs in uniform shades of gray, from steel-gray to dark gray. No color varieties or commercial varieties are distinguished. ## History and Name The mineral was first described in 1959 based on samples found in a mine in Černý Důl, Czech Republic. Its name honors the Czech mineralogist and crystallographer, Professor Jiří Novák (1902-1971) from Charles University in Prague. ## Uses Due to its extreme rarity, novákite has no industrial application. It is solely an object of scientific and collecting interest for specialized collectors of rare minerals.

Properties

Mohs hardness
3-3.5
Luster
Metallic
Streak
Black
Density
6.7
Transparency
Opaque
Crystal system
Monoclinic

Diagnostic features

## Identification Novákite can be identified by its steel-gray color, strong metallic luster, and black streak. It is relatively soft and heavy. It occurs in compact, granular aggregates, often in association with other arsenides and sulfides. ## Distinguishing from Similar Minerals It can be confused with other gray minerals with a metallic luster, such as arsenic, domeykite, or algodonite. It differs from arsenic by the lack of distinct cleavage. Distinguishing it from domeykite and algodonite, with which it often co-occurs, is very difficult without advanced chemical analyses (EDS/XRD), as they have similar physical properties. ## Crystal Forms Well-formed crystals are practically unknown. This mineral primarily forms massive, compact, or fine-grained aggregates embedded in the host rock.

Geological environment

## Genesis Novákite is a hydrothermal mineral. It forms in ore veins, mainly calcite veins, cutting through metamorphic rocks. Its crystallization occurs under low to medium temperature conditions from solutions rich in copper, silver, and arsenic. ## Mineral Associations It most commonly co-occurs with other copper arsenides, such as domeykite and koutekite, as well as native arsenic, native silver, chalcocite, bornite, and calcite. ## Localities The most important and classic occurrence (type locality) is Černý Důl in the Hradec Králové region of the Czech Republic. This is the only confirmed and well-documented locality for this mineral in the world.

Rarity

Very rare

For collectors

## Quality Criteria Novákite's collector appeal is defined primarily by the richness of its aggregates and their purity. The most valued specimens are those where the mineral forms distinct, abundant aggregates with a fresh, metallic luster, preferably in association with other rare arsenides. The size of the specimen and the contrast with the surrounding rock (most often white calcite) also increase its value. ## Popular Localities The only source of collector specimens is the historical type locality in Černý Důl, Czech Republic. Material from this location is extremely difficult to acquire and appears on the market very sporadically.

Care and storage

## Cleaning Novákite specimens should only be dry-cleaned, using a soft brush to remove dust. Contact with water or chemicals can lead to oxidation and permanent surface damage. ## What to Avoid Contact with water, acids, detergents, and other chemicals should be strictly avoided. The mineral is sensitive to moisture and atmospheric oxygen, which can cause it to tarnish and develop dark coatings. It should not be heated or exposed to prolonged sunlight. ## Storage It is recommended to store specimens in airtight, acid-free boxes or containers (so-called "membrane boxes") away from moisture and contaminants. Consider using desiccants in the collection storage area.

External references

Sources

Read more