Mineral of the Month - Vanadinite
Posted by Site Moderator Webmaster on Tuesday, May 11, 2010 Under: Mineral of the Month
Vanadinite belongs to the apatite group of phosphates and has the chemical formula Pb5(VO4)3Cl. It is one of the main industrial ores of the metal vanadium and a minor source of lead. It is an uncommon mineral, occurring as the result of chemical alterations to a pre-existing material. It is found in association with the lead sulfide, galena, as well as wulfenite, limonite, and barite. It was first discovered in 1801 in Mexico by the Spanish mineralogist Andres Manual del Rio, and was eventually named vanadinite because of its high vanadium content.
As well as Arizona, Mexico, Austria, Spain and Morocco, good specimens of vanadinite are found in southern Africa. Vanadinite has perfect hexagonal crystals, which are either barrel shaped or flat and tabular, which, along with its colour, makes the mineral easily recognisable. The distinctive colour of the crystals is usually a bright red, but they can also be darker, ranging from gray to a caramel-brown. Vanadinite has a hardness of 3 and an SG of 6.6+, which is very heavy for a translucent mineral, and its streak is white. In South Africa beautiful crystals have been found in the Ottoshoop district, but the largest vanadinite crystals in the world were collected at the Abenab mine in the Otavi mountainland of Namibia during the years 1922 to 1958. These were over 12 cm long, and most were covered with a grey coating of descloisite over the bright red inner core. More recently specimens have come from the Berg Aukas mine. For a short period in Zimbabwe in the 1960s, specimens of vanadinite covering drusy quartz were also collected and sold as mineral specimens. JW
References: Wikipedia, Field Guide to Rocks & Minerals of Southern Africa – Bruce Cairncross
MINERALS OF MOROCCO
In November last year, I had the good fortune to go with Jan to a conference in Marrakech and so, while he was working, I took the opportunity to the sights and seek out local minerals. Mineral shops per se are few and far between and those you do find are primarily selling fossils, such as ammonites and orthoceras, and small white calcite and quartz geodes, and aragonite items. The souks feature metallic pink and blue crystal filled geodes, unlike anything I have ever seen before.
We got lost in the souk our first night in town because of minerals. I enquired about vanadinite at a stall that sported a few fossils and metallic geodes and was shown a dull specimen. When I asked for better quality, the owner told me to wait and rushed off into the bustling rabbit warren and returned 5 minutes later with two far finer pieces. As I was interested in them, the protracted bargaining session began, and our companions disappeared into the multi-coloured crowd. I only had limited cash that first day, but ultimately it was accepted as sufficient for my purchases, and left us just enough money for supper. We hurried on merrily along the busy pathways in search of the rest of the party, but then came out into the open night sky far from where we thought we were - even my personal GPS was completely confused – and it was necessary to get someone to lead us to the designated meeting place. However, this experience was well worthwhile, as I didn’t see such bright coloured specimens again for the whole week.
A day’s outing from Marrakech, over the High Atlas Mountains, to Ouazazate, an oasis in the desert, also showed us more of the Moroccan mineral world. A pit stop was made at a good mineral shop high on the Tizi n Tichka pass, where outside there was a display of large ammonites, and colourless quartz geodes. The inside was packed with gypsum roses, smaller ammonites, orthoceras, colourless geodes galore, and a few black ball shaped geodes. An attractive dense purple “amethyst” geode also caught the eye. The black balls turned out to be clay, lined with metallic silver, blocky crystals, which have some connection to cobalt but I have yet to discover what. The shopkeeper admitted freely that certain items were fake, and then when he realised we were looking for better quality specimens, showed us a tray of vanadinite he had hidden under the counter. They were the only items of colour in the whole shop apart from the dyed geodes. One more piece was purchased here.
This seemed to be the extent of what I could find in the way of minerals, until the last free afternoon when I took myself off to the Place el Jemaa el Fna for a photography session. Not wanting to get lost again in the souk I looked only at the shops on the edges of the square, and by chance went up an alley that had minerals outside one of the shops. This stall proved to be a small room selling only minerals. Again it contained predominantly colourless geodes, and fossils, but one table had a few small boxes of orangey aragonite crystals, gemmy epidote, fine grained but very blue azurite, and vanadinite on barite. I was also shown a seemingly smooth black geode containing quartz with a strong vein of pyrite running across it. It was very heavy, but I don’t know what it was. I took my time talking to the shopkeeper, and selecting some possible specimens to be part of the bargaining process. She in turn produced two pieces of pink colbaltian calcite from under the counter, and also a box of very weathered, smooth and rounded meteorites. This included her personal prized giant that almost filled my hand. The meteorites and fossils come from the western desert between Marrakech and Agadir, and are found in the areas where phosphates are mined for export. Vanadinite is mined in the desert to the far east of Morocco, in the areas around Mibladen, Meknes, and Medelt and as far down south as Taouz. A lot of cobalt is also exported from mines in the High Atlas.
A superb example of Moroccan craftsmanship that we saw in Casablanca is the Hassan II Mosque, which was completed in 1993 at a cost of 80 million euros. Built on 12 hectares of reclaimed land at the edge of the sea, it now claims to have the highest minaret in the world from the top of which a laser ray directed towards Mecca shines for up to 30 km. The vast doors that open onto the prayer room are titanium (to avoid rusting because of the sea air), and the whole building itself is made of an array of local granites and marbles, carved and inlaid in places with colourful mosaics.
A week is nowhere near enough time to spend in this charming and colourful country, but I was still very happy with the mineral specimens I found – on the whole that is! JW
As well as Arizona, Mexico, Austria, Spain and Morocco, good specimens of vanadinite are found in southern Africa. Vanadinite has perfect hexagonal crystals, which are either barrel shaped or flat and tabular, which, along with its colour, makes the mineral easily recognisable. The distinctive colour of the crystals is usually a bright red, but they can also be darker, ranging from gray to a caramel-brown. Vanadinite has a hardness of 3 and an SG of 6.6+, which is very heavy for a translucent mineral, and its streak is white. In South Africa beautiful crystals have been found in the Ottoshoop district, but the largest vanadinite crystals in the world were collected at the Abenab mine in the Otavi mountainland of Namibia during the years 1922 to 1958. These were over 12 cm long, and most were covered with a grey coating of descloisite over the bright red inner core. More recently specimens have come from the Berg Aukas mine. For a short period in Zimbabwe in the 1960s, specimens of vanadinite covering drusy quartz were also collected and sold as mineral specimens. JW
References: Wikipedia, Field Guide to Rocks & Minerals of Southern Africa – Bruce Cairncross
In November last year, I had the good fortune to go with Jan to a conference in Marrakech and so, while he was working, I took the opportunity to the sights and seek out local minerals. Mineral shops per se are few and far between and those you do find are primarily selling fossils, such as ammonites and orthoceras, and small white calcite and quartz geodes, and aragonite items. The souks feature metallic pink and blue crystal filled geodes, unlike anything I have ever seen before.
We got lost in the souk our first night in town because of minerals. I enquired about vanadinite at a stall that sported a few fossils and metallic geodes and was shown a dull specimen. When I asked for better quality, the owner told me to wait and rushed off into the bustling rabbit warren and returned 5 minutes later with two far finer pieces. As I was interested in them, the protracted bargaining session began, and our companions disappeared into the multi-coloured crowd. I only had limited cash that first day, but ultimately it was accepted as sufficient for my purchases, and left us just enough money for supper. We hurried on merrily along the busy pathways in search of the rest of the party, but then came out into the open night sky far from where we thought we were - even my personal GPS was completely confused – and it was necessary to get someone to lead us to the designated meeting place. However, this experience was well worthwhile, as I didn’t see such bright coloured specimens again for the whole week.
A day’s outing from Marrakech, over the High Atlas Mountains, to Ouazazate, an oasis in the desert, also showed us more of the Moroccan mineral world. A pit stop was made at a good mineral shop high on the Tizi n Tichka pass, where outside there was a display of large ammonites, and colourless quartz geodes. The inside was packed with gypsum roses, smaller ammonites, orthoceras, colourless geodes galore, and a few black ball shaped geodes. An attractive dense purple “amethyst” geode also caught the eye. The black balls turned out to be clay, lined with metallic silver, blocky crystals, which have some connection to cobalt but I have yet to discover what. The shopkeeper admitted freely that certain items were fake, and then when he realised we were looking for better quality specimens, showed us a tray of vanadinite he had hidden under the counter. They were the only items of colour in the whole shop apart from the dyed geodes. One more piece was purchased here.
This seemed to be the extent of what I could find in the way of minerals, until the last free afternoon when I took myself off to the Place el Jemaa el Fna for a photography session. Not wanting to get lost again in the souk I looked only at the shops on the edges of the square, and by chance went up an alley that had minerals outside one of the shops. This stall proved to be a small room selling only minerals. Again it contained predominantly colourless geodes, and fossils, but one table had a few small boxes of orangey aragonite crystals, gemmy epidote, fine grained but very blue azurite, and vanadinite on barite. I was also shown a seemingly smooth black geode containing quartz with a strong vein of pyrite running across it. It was very heavy, but I don’t know what it was. I took my time talking to the shopkeeper, and selecting some possible specimens to be part of the bargaining process. She in turn produced two pieces of pink colbaltian calcite from under the counter, and also a box of very weathered, smooth and rounded meteorites. This included her personal prized giant that almost filled my hand. The meteorites and fossils come from the western desert between Marrakech and Agadir, and are found in the areas where phosphates are mined for export. Vanadinite is mined in the desert to the far east of Morocco, in the areas around Mibladen, Meknes, and Medelt and as far down south as Taouz. A lot of cobalt is also exported from mines in the High Atlas.
A superb example of Moroccan craftsmanship that we saw in Casablanca is the Hassan II Mosque, which was completed in 1993 at a cost of 80 million euros. Built on 12 hectares of reclaimed land at the edge of the sea, it now claims to have the highest minaret in the world from the top of which a laser ray directed towards Mecca shines for up to 30 km. The vast doors that open onto the prayer room are titanium (to avoid rusting because of the sea air), and the whole building itself is made of an array of local granites and marbles, carved and inlaid in places with colourful mosaics.
The Hassan II Mosque in Casablanca
A week is nowhere near enough time to spend in this charming and colourful country, but I was still very happy with the mineral specimens I found – on the whole that is! JW
In : Mineral of the Month
