Esfalerita Marmatita
Esfalerita is a mineral with formula (Zn,Fe)S + FeS₂, in the Sulfuros group. This specimen comes from Stan Terg Mine (Stari Trg), Trepča Complex, Mitrovica, Mitrovica District, Kosovo and joined the Terrium collection in 2025.
Description
La Hermanita Redentora Well-developed marmatite sphalerite crystals with intense lustre on a massive pyrite matrix pseudomorphous after pyrrhotite, with its hexagonal crystals. Accompanied by small calcite inclusions reactive under UV light.
History of this specimen
I had a larger piece of the same association (marmatite sphalerite on pyrite pseudomorph after pyrrhotite) which, when I washed it with water, developed an oxide patina that dulled its lustre. I was very sorry and looked for another: I found this second one, much smaller but much more attractive. And lesson learnt.
About Esfalerita
On pyrrhotite: it has been nicknamed "magnetic pyrite". Bronze to brown in colour, darker than pyrite. It tarnishes (oxidises) much more quickly, acquiring iridescent or brown tones. It rarely forms cubes; it commonly occurs as hexagonal crystals or granular masses. Structurally it is "defective", lacking some iron, which imparts magnetism. The other two minerals are zinc and iron sulphides: sphalerite is the principal ore of zinc; pyrite is the most abundant iron sulphide. Marmatite sphalerite is dark because it is iron-rich. At Trepča it occurs as complex crystals with well-developed faces and adamantine lustre.
About the locality
The Trepča mining complex, in Mitrovica (Kosovo), is one of the largest polymetallic deposits in south-eastern Europe. Active since the Yugoslav period, it produces quartz, galena, sphalerite, pyrite, arsenopyrite and calcite.
Technical data
- Catalogue No.
- 0274
- Composition
- (Zn,Fe)S + FeS₂
- Name
- Esfalerita
- Variety
- Marmatita
- Group
- Sulfuros
- Category
- Cresta Montis
- Matrix
- Pirita pseudomorfa tras pirrotita
- Associations
- calcita
- Mine
- Stan Terg Mine (Stari Trg)
- District / Municipality
- Trepča Complex
- Province
- Mitrovica
- Region
- Mitrovica District
- Country
- Kosovo
- Size (cm)
- 8 x 6 x 3
- Weight
- 320 g
- Acquired
- 2025
- Etymology
- The name of this mineral preserves an old miners' insult. German miners called it "Blende" (from the verb blenden, to deceive) because its lustre promised valuable metals (lead or silver), but smelting yielded nothing of value. In 1847 it was formalised as "sphalerite", from the Greek "sphaleros", literally "treacherous". It is a linguistic counterpart to pitchblende; both bear pejorative names born of miners' frustration. The variety marmatite takes its name from Marmato (Colombia).
- Quality
- Notable
- Value trend
- Estable
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