Horákite

Properties

Mohs hardness

2

Luster

Vitreous

Streak

Light yellow

Density

6.358

Cleavage

on {100}

Transparency

Transparent,Translucent

Crystal system

Monoclinic

Diagnostic features

## Identification Identifying horákite under amateur conditions is practically impossible. Identification requires advanced analytical methods such as X-ray diffraction (XRD) and chemical analysis (EDS/WDS). Preliminary indications may include its light yellow to greenish-yellow color, tabular microcrystal form, and co-occurrence with other secondary uranium and bismuth minerals in uraninite veins. Strong radioactivity is a key feature, but common to many uranium minerals. ## Distinguishing from Similar Minerals Horákite can be confused with many other secondary uranyl minerals, such as phosphuranylite, meta-autunite, saleeite, or torbernite, which have similar colors and often form small, tabular crystals. Visual distinction without specialized equipment is unfeasible. ## Crystal Forms Crystals are very small, usually not exceeding 0.2 mm. They have the form of thin tablets or blades, often flattened parallel to the {100} cleavage plane. They form radial aggregates, rosettes, or irregular clusters on the host rock.

Geological environment

## Genesis Horákite is a secondary mineral that forms in the oxidation zone of polymetallic hydrothermal deposits rich in uranium and bismuth. It forms as a result of weathering and alteration of primary uraninite and native bismuth ores in the presence of phosphate and arsenate-bearing solutions. ## Mineral Associations This mineral occurs in association with other secondary uranium and bismuth minerals. At the type locality, its co-occurrence with beckerelite, bismutite, kasolite, metatorbernite, schoepite, torbernite, uranophane, and walpurgite has been observed. ## Localities The only confirmed and described occurrence of horákite in the world is its type locality – the historic Rovnost Mine in Jáchymov (formerly St. Joachimsthal), Czech Republic.

Rarity

Extremely rare

For collectors

## Quality Criteria As a microscopic mineral, the main criterion for evaluating a specimen is the abundance and quality of crystals visible under magnification. Specimens with numerous, well-formed, sharp crystals forming aesthetic aggregates are most valued. Color contrast with the rock matrix and the presence of rare associated minerals are also important. ## Popular Localities The only source of horákite specimens is its type locality – the Rovnost Mine in Jáchymov, Czech Republic. All specimens available on the collector's market originate from this single location.

Care and storage

## Cleaning Horákite specimens, as extremely rare and fragile microcrystals, should generally not be mechanically cleaned. Any attempt to use a brush, even the softest, risks irreversible damage to the crystals. If cleaning is absolutely necessary, compressed air can be carefully used from a safe distance to remove loose dust particles. ## What to Avoid Contact with water, acids, bases, and all chemical solvents must be strictly avoided. Avoid vibrations, shocks, and temperature changes. As a strongly radioactive mineral, it requires special precautions – direct, prolonged contact should be avoided, and it should be stored away from areas of permanent human habitation. ## Storage Specimens should be stored exclusively in specialized, sealed containers designed for radioactive minerals, preferably in "micromount" boxes to protect against mechanical damage. The container should be clearly labeled as radioactive material. Store in a dry place, away from other minerals that could be damaged by radiation.

External references

• https://www.mindat.org/min-51973.html

Sources

• Mindat - Horákite
• IMA Mineral List (CNMNC)