Zeolites @ Portugal is a brief introduction of the main places in Portugal where some Rocks present zeolitization or in its genesis includes Zeolites.

The main area where some rocks exhibit these characteristics belongs to the Lisbon volcanic complex where igneous activity has been developed in the open North Atlantic. The Lisbon volcanic complex covers an extent of about 200km2 between Lisbon, Sintra, Mafra and Runa. It is installed between the upper Cretaceous and lower Eocene, there are 72 million years. It presents various types of structures (chimneys, drained, sills, dikes, etc..) and rocks (basalts, pyroclastics, breccias, trachytes, etc..). Predominates in general basalts, gabbros and some volcanites.



1- A classic place and with featured of this complex is Lomba dos Pianos where Dolerites in the form of sills emerge in north of Sintra between the beaches of Samarra and Magoito 3km along with cuts in cliffs above the sea and with maximum thickness of 20 meters. In this place the rocks exhibit a curious columnar joints referred to the name of "Pianos" – Church organ and in certain sites have areas of intense zeolitization, with globular and radiated structures with white and orange colors, which were identified radiographically Natrolite and Thomsonite, and in times labored until the early 80's a quarry at this location and that unfortunately is presently serving as a landfill for inert. Today one can still collect some samples, however it is quite dangerous due to the bursting of the sea on the rocks and access to mineralization on the slopes.


Over the years have taken some samples, some of which quarry when this worked. I visually identified Natrolite, Thomsonite, Analcime, Stilbite, Heulandite and accessories as the Smectite group and Calcite.


















The Zeolites most common in this site is the association of massive and radiated epistaxis of orange Natrolite with white Thomsonite. In the cavities the Natrolite presented in blood capillaries colorless prisms on Thomsonite or Analcime accompanying sometimes Calcite and Smectite. The Thomsonite when alone, presented in plates, radiated groups and white blood cells and is rich in calcium.


















The Analcime presented in cavities with groups of crystals with Trapezohedron configuration and usually accompanying with Natrolite, Calcite, Smectite and more rarely with Stilbite. It is common the Natrolite crystals penetrate in Analcime and Calcite crystals.


















The Stilbite and Heulandite of this occurrence is less common. The samples that i got with developed crystals were collected at the beginning of the 80s when the quarry was active. The Stilbite presents with an orange-reddish color with characteristic crystals to 1cm and often accompanies Analcime. The Heulandite develops prisms (010) up to 1cm and almost always accompanies with Calcite and more rarely with Stilbite.




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2- The municipality of Oeiras in Lisbon district belonging to the Lisbon volcanic complex is another place where to the demographic explosion due to the construction of road structures, allows sometimes over time uncovered some mineralized rocks with zeolites. In this context there are an interesting place close of Valejas village where the basalt is presented in pads with microscope texture and zeolitizated.


This zeolitizated strip has approximately 800x30 meters and begins downstream of Valejas bridge along the Jamor river. This strip has a direction more or less NNE-SSW and is crossed by the Queluz road nº 117. The zeolitization are in amygdaloid groups and amygdalas more than 5cm are exceptional. The mineralization basically contains crystallization of Analcime, Natrolite, Thomsonite and Calcite.


















Here the Analcime has more "body" compared with Analcime of Lomba dos Pianos and presents sometimes lightly colored of pink and set on Trapezohedron. Fill the walls or all space of amygdalas with Calcite. Almost always accompanies with Natrolite and sometimes Thomsonite and Smectite.


















The Natrolite presented in colorless prisms and accompany with Analcime, Calcite or Thomsonite and sometimes their crystals are coated with Smectite. In smaller amygdalas can present itself with intercrossing crystals.


















The Thomsonite presents globular or radiated, colorless, white or pink and form epistaxis with Natrolite and normaly accompanies Calcite or Analcime.


Near to Valejas and in Queijas village when made the road structures to access the National Stadium, stood uncovered some cavities with nice pink Natrolite. The municipality of Oeiras has other representations with Heulandite, Thomsonite, Mordenite etc. At the same Lisbon volcanic complex in municipality of Sintra in the parishes of Terrugem and Montelavar-(Penedo do Lagarto quarry) has an interesting zeolitization with representations of Thomsonite, Mordenite and Trydimite. Other interesting places of this volcanic complex is Penedo do Lexim near Mafra and Mount Suimo near Belas with featured representation of Pyrope.
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3 - Another site with some representative zeolites is most southern in Algarve with Massif Eruptive of Monchique. This massif is intrusive and alkaline in nature. His activity began at 72 million years ago with the opening of North Atlantic in Cretaceous and covers an area of 80km2. It consists almost entirely of nepheline-syenite rocks, aplite-pegmatite nepheline veins, dikes and veins composed essentially of syenite, phonolite and lamprophyres veins, breccias and igneous gabbros. The massive intrusion caused a halo of metamorphism contact with a corneal thickness of about 200 meters.
The syenitic rocks are composed as major minerals: Alkali feldspar, nepheline, pyroxene and mica. The accessory minerals include analcime, apatite, calcite, cancrinite, titanite, fluorite, lavenite, natrolite, pyrite, pyrochlore, rosenbuschite, rutile, sodalite, tourmaline, zircon and wölerite. The crystal growth is relatively rare because these rocks are quite compact and poor in cavities. Sometimes pegmatite veins or cavities gives crystals, generally millimetric or sub-millimetric of analcime, natrolite, fluorite, aegirine, ancylite-Ce, chalcopyrite, magnetite, pyrite, pyrrhotite, galena, sodalite and zircon. Of all these the most notable are those that refer to minerals of zeolites group with dimensions that reach far superior to other crystals such as natrolite, gonnardite and analcime. The study and collection of these minerals is through an active quarry (Lugar da Nave quarry) and another currently closed (Palmeira nº 2 quarry), both located near Monchique village.




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The analcime is a mineral that stands out to other minerals by the size of the crystals that may reach the cm. The crystals are characteristic and are normally in groups of white or translucent lightly colored pink. Accompanies with alkali feldspar, natrolite, aegirine, pyrite, calcite etc. The specimens collected in November of 2009 in Palmeira nº 2 quarry and were the object of study, revealed some minerals like strontianite, gaidonnayite, burbankite and hilairite.



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The natrolite of Lugar da Nave quarry presented in groups on how to elongate prisms up to 10cm, completely coating the cavities. Form epistaxis with gonnardite through the outer layer of the crystals with white color, the interior being colorless. With dehydration becomes completely gonnardite with the drawback of destroying to the little touch. Natrolite samples collected from this quarry in 1976, have short crystals to 0.5 cm, well-defined symmetry and translucent. Bring references of gonnardite. The natrolite of Palmeira nº 2 quarry presents groups of elongated colorless prisms and second Volker Betz with the possibility of two different growth stages. Accompanies with the mineral paragenesis of the above.


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4 - A zeolitization site who once had an active quarry that was grounded and that today there is no evidence of it, was near the Catulão mill in the Gaeiras village, Óbidos in Leiria district. The quarry operated a strike length of dolerite zeolitizated and geologically fits in typhonic valley of Caldas da Rainha. This vein belongs to a chimney whose magmatic phenomenon is related to the eruptive activity of Extremadura which includes the Volcanic Complex of Lisbon. The eruptive rocks of this typhonic valley including Gaeiras vein, were studied in 1956 by M. Montenegro de Andrade and G. Zbyszewski.
M. Montenegro de Andrade in 1977 drafted an article about a beautiful specimen of Natrolite from a dolerite strike lengh of Gaeiras and here is the reference.
To finish there are a reference to some articles of non-Portuguese authors who reported to occur Pollucite in pegmatites of Mesquitela - Viseu district, Gonçalo - Guarda district and Arga mountain. Laumontite occurrence of a pegmatite in Forno de Algodres. Another article in Dutch language concerning the occurrence of Chabazite and Phillipsite in Madeira island.
A subject that intrigues me is there no a study or reference of zeolites in Azores islands with this volcanic origin.
How should calculate this article is subject to various interventions update. Any suggestions and if anyone wants to help in building this article with photos or other reference, accepted willingly, in which I will mention to the author.
Thank you all.

Martins da Pedra

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