By Branko Rieck
General Appearance
The mineral Adamite is one of the signature minerals from the Lavrion Mining District. More often than not, people think that adamite is named for the Adami mines in the Plaka area, but this is not so. It is actually named after Gilbert Joseph Adam (April 7, 1795 Seine-et-Marne, Fontainbleau, France – 1881 Paris, France), who provided the type-specimens (from Chañarcillo, Copiapó Province, Chile).
Adamite appears in a wide variety of shapes, colors and aggregates. While the colorless, yellow or pink varieties are not easily confused with other minerals, the green (Cu-bearing) variety is easily mistaken for zincolivenite or olivenite (and vice-versa). Even after 35 years of collecting minerals from the Lavrion Mining District, the author still relies on analysis and not visual appearance to distinguish it from its close relatives (and possibly conichalcite as well). Adamite is found as individual, single crystals, radial sprays, bow-tie shaped, erratic growths and crusts, that often show zonal growth and may reach 2 cm in thickness.
Typical crystal shapes of adamite:
Paragenesis
There are actually two different types of occurrence.
One is typically on marble host rock, with or without secondary calcite crystals directly on the adamite. This paragenesis is rather “poor”. Usually you find – apart from calcite and aragonite – some small smithsonite rice grains, chalcophanite if you are lucky, but not much else worth mentioning. However, this paragenesis has yielded some of the most beautiful and spectacular specimens ever to be found in Lavrion. Kostas Kapellas, a Greek collector from Agios Konstantinos, not too long ago (2015) found a series of pockets containing adamite crystals up to 25 mm in length – not the world’s largest, but specimens beautiful to behold. Generally, the adamite in this paragenesis is pretty pure, containing less than 2% metals other than zinc. The author has come across one exception to this rule though: at the third level of the Jean Baptiste area a small locality yielded deep purple adamite of the manganese-bearing variety. These contained up to 9% Mn replacing Zn.
The second type of paragenesis is much richer in variety but the crystals are usually much smaller – reaching 2 or 3 mm, but commonly less than 1 mm. The host for these adamites is usually a gossan matrix and may contain 30 or 40 different other species.
Localities
Adamite in all its varieties is found throughout the Lavrion Mining District. Most prolific however is the area of the Kamariza Mines.
Adamite is found in various chemical varieties: aluminum-bearing, cobalt-bearing, copper-bearing, manganese-bearing and nickel-bearing. On Mindat and in most of the relevant literature the “old” names (e.g.: nickeloan adamite) are given instead of the IMA-approved naming scheme (e.g.: nickel-bearing adamite).
Alumino Adamite
Among the chemical varieties of adamite this one is somewhat special, as in this case divalent zinc is replaced by trivalent aluminum which requires a different local charge balance to be in place (e.g. OH being replaced by O).
By determination of the unit-cell parameters (e.g. by PXRD or SXRD) the aluminum-bearing variety of adamite can be distinguished both from copper-bearing adamite and from adamite that contains submicroscopic inclusions of aluminum-rich minerals (e.g.: gibbsite). The latter is “dangerous” insofar, as it may deceive the unwary into thinking of an aluminum content of the hosting adamite. Pure adamite has unit-cell parameters given as a = 8.304 Å, b = 8.524 Å, c = 6.036 Å. While in copper-bearing adamite b and c become smaller and a bigger, in the aluminum bearing variety all three become smaller (a = 8.29 Å, b = 8.48 Å, c = 6.00 Å in a sample of the composition Al0.14Fe0.06Zn1.80(AsO4)(OH)). Preliminary work suggests that the aluminum content is restricted to the ZnO4(OH) trigonal bipyramid within the lattice.
This variety of adamite is very rare, both in Lavrion and in the world in general. After 35 years of collecting and more than 400 analyses of adamite I dare say that there is only one locality in Lavrion that yields this variety: A small occurrence in the Serpieri #5 Mine. It is also possible, that material from this outcrop may be found at the Kamariza dump, however I cannot confirm this from own experience. I believe that all samples of “Alumino Adamite” from other localities are either not of the aluminum-bearing variety of assigned to the wrong locality.
On most specimen I have seen there is a very thin layer of gibbsite directly on the limonitic matrix. On this layer there is either hydrozincite, zincaluminite or powdery hemimorphite.
Hemimorphite is always (at least on my specimen) accompanied by glassy allophane and shows no crystal faces at all. The latest mineral to form in this sequence is barahonaite-(Al).
Hydrozincite shows a weak white fluorescence under SW UV light and shows bubbles forming in vinegar (you need to remove a small, pure fragment from the specimen and watch under the microscope, otherwise carbonate from the matrix will give you false results). Very interesting is the occurrence of the rare mineral sclarite as a late-stage product.
Zincaluminite usually displays hexagonal crystal faces and more “3-dimensional” aggregates.
