Schafarzikite
Chemical formula: Fe²⁺Sb³⁺₂O₄
A rare iron and antimony oxide, forming characteristic, acicular crystals of reddish-brown color and metallic luster.
Properties
- Mohs hardness
- 3.5
- Color
- Red-brown to red, black; yellow in transmitted light
- Luster
- Metallic, Sub-Metallic
- Streak
- Brown
- Density
- 4.3
- Cleavage
- On {110}, perfect; on {100}, very good; on {001}, in traces.
- Fracture
- None observed
- Transparency
- Opaque
- Crystal system
- Tetragonal
Diagnostic features
## Identification Schafarzite can be identified by its characteristic habit – long, acicular or prismatic crystals, often forming radial aggregates. Key features also include its reddish-brown to black color, strong metallic luster, and reddish-brown streak. Its occurrence in hydrothermal antimony deposits is also an important clue. ## Distinguishing from Similar Minerals Schafarzite is sometimes confused with other oxides or sulfides of similar appearance, such as stibnite or rutile. It differs from stibnite by its hardness (stibnite is much softer, about 2 on the Mohs scale) and streak color (stibnite has a grayish-black streak). Rutile is much harder (6-6.5) and has a lighter streak. Kermesite, though similar in color, has a different habit and is softer. ## Crystal Forms Schafarzite crystals are typically elongated, prismatic along the [001] axis, often with a square or octagonal cross-section. They commonly occur as acicular aggregates, radial clusters, or tangled fibrous masses. Single, well-formed crystals are less common.
Geological environment
## Genesis Schafarzite is a secondary mineral, formed in the oxidation zones of hydrothermal antimony ore deposits. It forms as a result of the alteration of primary antimony minerals, such as stibnite, under low-temperature conditions. ## Mineral Associations This mineral often co-occurs with other secondary antimony minerals. Its typical associates include valentinite, senarmontite, kermesite, as well as primary stibnite, from which it forms. It can also occur in association with quartz, calcite, or barite. ## Localities The most important and classic locality (locus typicus) is Pernek in the Little Carpathians, Slovakia. Other known occurrences include the Cetine di Cotorniano mine in Tuscany (Italy), where excellent specimens were found, as well as localities in Germany (Arnsberg), Romania (Baia Sprie), and Bolivia.
Rarity
Rare
For collectors
## Quality Criteria The most valued by collectors are specimens with well-formed, sharply terminated crystals of intense, reddish-brown color and strong metallic luster. Particularly sought after are radial aggregates of acicular crystals, forming aesthetic "suns" or "hedgehogs" on the rock matrix. The size of the crystals and the absence of mechanical damage are also important. ## Popular Localities Classic and most desirable specimens come from historical finds in Pernek, Slovakia, and from the Cetine di Cotorniano mine in Italy. Specimens from these localities, especially well-preserved ones, fetch high prices on the collector's market and are a highlight of advanced systematic collections.
Care and storage
## Cleaning Schafarzite specimens should only be cleaned mechanically, using a soft brush to remove dust. Due to its fragility and potential reactivity, contact with water and any chemical agents should be avoided. For heavier dirt, compressed air can be used. ## What to Avoid Contact with water, acids, detergents, and other chemicals that may cause oxidation or damage to the crystal surface must be absolutely avoided. The mineral is brittle, so it must be protected from impacts and falls. It should not be heated or exposed to prolonged moisture. ## Storage It is recommended to store specimens in a dry place, preferably in closed collector boxes or display cases away from moisture. To prevent mechanical damage, each specimen should be isolated from other minerals.