Tzeferisite

Tzeferisite
Damianos Mine, Dimoliaki mines, Dimoliaki, Lavrion Mining District, Lavreotiki, East Attica, Attica, Greece (Lavrion Type locality)
General
Category	Sulfate mineral
Formula	CaZn8(SO4)2(OH)12Cl2(H2O)9
IMA symbol	Τze
Strunz classification	7.DF. 7 : Sulfates (selenates, tellurates, chromates, molybdates, wolframates) D : Sulfates (selenates, etc.) with additional anions, with H2O F : With large and medium-sized cations
Crystal system	Trigonal
Crystal class	3m (3 2/m) - Hexagonal Scalenohedral
Space group	R3c
Unit cell	4,112.46 Å3
Identification
Colour	White, colorless
Lustre	Vitreous
Diaphaneity	Transparent
Other characteristics	Tzeferisite is not radioactive

Tzeferisite is a sulfate mineral with formula: CaZn₈(SO₄)₂(OH)₁₂Cl₂(H₂O)₉. It is the natural analog of the anthropogenic slag phase Ca_0.5Zn₄(SO₄)(OH)₆Cl·4.5H₂O that was first discovered in slag dumps at Val Varenna, Italy (formula halved and reformulated to show the similarities to the other compounds discussed; (Burns et al., 1998)[1]

Gordaite, NaZn₄(SO₄)(OH)₆Cl·6H₂O (Adiwidjaja et al., 1997; Zhu et al., 1997) and Fabritzite Zn_0.5Zn₄(SO₄)(OH)₆Cl·3H₂O (formula halved and reformulated to show the difference between the two octahedrally Zn atoms), are closely related. All three compounds share the same brucite-type octahedral sheet with attached Zn (OH)₃Cl tetrahedra, only the charge-balancing interlayer cation is different (0.5Zn²⁺ vs Na⁺ and 0.5Ca²⁺, respectively).

Tzeferisite is a supergene mineral, member of Namuwite Group. Chlorine-rich solutions that caused the leaching of Cd from primary sphalerite and the deposition of secondary, fine-grained greenockite were also responsible for the deposition of tzeferisite. Associated minerals include sphalerite, galenite, greenockite, hemimorphite, fabritzite, gypsum, calcite, and dolomite.

Appearance, composition and crystal structure

[επεξεργασία] Tzeferisite forms thin, colorless to white, hexagonal platelets (up to 250 µm in diameter and up to 25 µm thick) that are aggregated in clusters or evenly distributed on the matrix. It is white or colorless with a vitreous luster. The "yellow" impression often seen is due to the greenockite-bearing matrix or due to microinclusions of greenockite in tzeferisite itself. Associated minerals are sphalerite, galenite, greenockite, hemimorphite, fabritzite, gypsum, calcite, dolomite.

Table 1: Chemical data (in wt%) for tzeferisite.

Constituent	1) Mean	2) Range
SO3	13.26	13.03 – 13.43
CaCl₂	9.16	8.90 – 9.43
ZnO	54.25	53.96 – 54.50
H₂O*	22.66
Total	99.33

* from crystal-structure determination since not enough material is available for a direct determination.

Chemical analysis by electron microprobe resulted in the empirical formula Ca₀․₉₉Zn₈․₀₂(SO₄)₂(OH)₁₂Cl₁․₉₈(H₂O)₉, calculated on the basis of 30 H atoms per formula unit (apfu). The simplified formula is CaZn₈(SO₄)₂(OH)₁₂Cl₂(H₂O)₉

The ideal formula is CaZn₈(SO₄)₂(OH)₁₂Cl₂(H₂O)₉, which requires SO₃ 13.43 wt.%, H₂O 22.66 wt.%, CaCl₂ 9.31 wt.%, ZnO 54.60 wt.%, Total 100 wt.%.

The mineral tzeferisite from the Lavrion mining district, Attica, Greece and the synthetic compound from the slag dumps at val Varenna, Italy exhibit the same crystal structure. Crystal data for tzeferisite, space group R3c, are listed on the right table. Unit cell dimensions are a = 8.3693Å, b = 8.3693Å, c = 67.794 Å, V = 4112.5 Å3, close to those reported for the slag phase (Burns et al., 1998).

Occurrences

[επεξεργασία] The only type locality for tzeferisite so far is the Damianos Mine, a small mine in the Charvalo area of the Dimoliaki subdistrict of Lavrion, Attica, Greece, poor in carbonate-replacement Pb-Zn-Ag ore, but with a surprisingly high Cd-Content of the Zn-ore. Tzeferisite was discovered by Dr. B. Rieck guided to the locality by Η. Katsaros who also helped with the sampling. Type material is conserved at the Natural History Museum, Vienna, Austria, catalogue no 02549.

The mineral Tzeferisite was named after Dr. Peter Tzeferis, a Greek mining engineer and Mineral Raw materials Gen. Director at the Hellenic Ministry of Environment and Energy, for being one of the driving forces enabling the scientific work on the Lavrion Mining District, Greece, on an international scale.

Dr Peter Tzeferis at the type locality in the Damianos Mine, Lavreotiki mining region. Well visible is the yellow greenockite.

The Lavrion Mining District, Attica, Greece, belongs to then most diverse localities on a worldwide scale. The most important minerals of Lavrion, from a financial point of view, were galena (PbS), cerussite (PbCO₃), sphalerite ([Zn,Fe]S), smithsonite (ZnCO₃) and Hematite (a-Fe₂O₃). However, besides above minerals that were mined in the past, the mines of Lavrion are host to at least 700 mineral species which comprise almost 12.8% of the known minerals worldwide.

These minerals form an important part of the World Mineralogical Heritage. They have no direct economic value, however, they have great aesthetic, historical, cultural, scientific and museum value. Amongst them, 25 are listed as Type Locality (TL) minerals of the Lavreotiki district, which were found and described from here for the first time i.e. Serpierite, Zincaluminite, Laurionite, Glaucocerinite, Ktenasite, Mereiterite, Natroglaucocerinite, Niedermayrite, Zincowoodwardite, Kapellasite, Attikaite, Zincolivenite, Drobecite, Kamarizaite, Agardite-(Nd), Hilarionite, Nickeltsumcorite, Katerinopoulosite, Prachařite, Voudourisite, Lazaridisite, Stergiouite , Katsarosite, Fabritzite and Tzeferisite.[2]

See also

• Mineralien Atlas
• "Tzeferisite". lavrion.gr. Retrieved 2025-06-15.
• Mindat.org
• Webmineral.com
• Contributions to the mineralogy of the Lavrion mining district, Greece