Calcofanita

Description

Elongate stalactitic habit. Dark brown colour with lighter earthy tones on the ridges. Surface covered by a compact, dull microbotryoidal texture, fine-grained. Very fragile.

About Calcofanita

Chalcophanite is a supergene hydrated manganese–zinc oxide. It can be described as a partly oxidised manganese-oxide framework, stabilised by zinc, with water incorporated in the structure. It forms crusts, botryoidal aggregates and stalactitic structures, with dull lustre and colours from brown to black. In its formula "(Zn,Mn²⁺)(Mn⁴⁺,Mn³⁺)₃O₇·3H₂O", the parentheses denote substitution: a crystallographic site may be occupied by more than one element. In the first group "(Zn,Mn²⁺)" the site is normally filled by zinc (Zn), with partial substitution by Mn²⁺. In the second group "(Mn⁴⁺,Mn³⁺)₃" there are three manganese positions that may host Mn⁴⁺ or Mn³⁺, coexisting in the crystal. The "O₇" are the oxygens forming the oxide framework, followed by three molecules of structural water "·3H₂O" integral to the mineral structure.

About the locality

Mina Haití, in Cartagena (Murcia), is a classic lead–zinc deposit with abundant secondary manganese oxides. There, uncommon and very fragile chalcophanite stalactites formed, produced by the circulation of manganese-rich solutions.

Technical data

Catalogue No.

0225

Composition

(Zn,Mn²⁺)(Mn⁴⁺,Mn³⁺)₃O₇·3H₂O

Name

Calcofanita

Group

Óxidos

Category

Estélites

Mine

Mina Haití

District / Municipality

El Estrecho de San Ginés

Province

Cartagena

Region

Región de Murcia

Country

España

Size (cm)

8 x 1.5 x 1.2

Weight

15 g

Acquired

2025

Etymology

From Greek "chalkos" (copper) and "phainesthai" (to appear), alluding to its visual resemblance to copper minerals.

Quality

Buena

Value trend

Estable

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