Showing category "Mineral of the Month" (Show all posts)

MINERAL OF THE MONTH – OLIVINE

Posted by Site Moderator Webmaster on Monday, July 27, 2020, In : Mineral of the Month

Duncan Miller

Olivine is the name given to both a mineral and a mineral group. The mineral olivine is an orthorhombic silicate with the relatively simple chemical formula of (Mg,Fe)₂[SiO₄]. It has a continuous range of composition between two end members, one magnesium-rich and the other iron-rich. The magnesium end member of the range is called forsterite (Mg₂SiO₄) and the iron end member is fayalite (Fe₂SiO₄). These distinct minerals form part of the olivine group, which also includes a mang...

New Barite Occurrence at Rosh Pinah Mine – Namibia

Posted by Site Moderator Webmaster on Saturday, March 25, 2017, In : Mineral of the Month

Author: Gisela Hinder, Rosh Pinah Geo Center, Rosh Pinah, Namibia

e-mail: gisela.hinder007@gmail.com

Rosh Pinah Mine is situated in the southwest of Namibia about 80 km east of Oranjemund. Rosh Pinah Mine became well known for its beautiful barites when a massive pocket of yellow to orange barite crystals was opened in 1989. It is said that these barites were the best ever found in Namibia.

In February 2017 new barite crystals were discovered at Rosh Pinah. Yellowish, unfortunately smallish, ...

A Bit about Blue Lace Chalcedony

Posted by Site Moderator Webmaster on Saturday, March 25, 2017, In : Mineral of the Month

Jo Wicht

Blue Lace “Agate” is found on the farm Ysterputs 254 (meaning iron holes) in Namibia. The mine is located adjacent to the “Blinkpan” (shining shallow lake) which can be seen to the west of the B1 highway about 80 km north of Vioolsdrift and Noordoewer, which are the border towns on either side of the Orange River between South African and Namibia.

Blue lace is not a true agate, but a chalcedony (microcrystalline quartz) laid down in a series of wavy bands, which gives it th...

Skorpion Zinc mine – another new mineral discovered

Posted by Site Moderator Webmaster on Saturday, May 2, 2015, In : Mineral of the Month

By Gisela Hinder

The Skorpion Zinc deposit is a complex, non-sulphide zinc orebody situated in a paleo-channel fill overlying rocks of the Port Nolloth Zone of the Gariep Belt about 20 km north-west of the little mining town Rosh Pinah, Karas Region, Namibia.

The Skorpion Zinc mine is the 8th largest Zinc Mine in the world and a world-class integrated mining and refinery operation. Skorpion Zinc's annual capacity is 150 000 tons of Special High Grade zinc.

The zinc-oxide is mainly hosted by arko...

The Colours of Quartz

Posted by Site Moderator Webmaster on Saturday, March 23, 2013, In : Mineral of the Month

The latest issue of The Journal of Gemmology has an excellent article by Ulrich Henn and Rainer Schultz-Güttler called ‘Review of some current coloured quartz varieties’. For those who don’t have access to this journal, published by the Gemmological Association of Great Britain, this is a short summary to help you distinguish the different varieties.

Uncut amethyst crystal, prasiolite (11,5 ct), rock crystal (20,5 ct), amethyst (2,5 ct), citrine (natural?) (8 ct), citrine and rose quar...

Jaspers - part 2

Posted by Site Moderator Webmaster on Saturday, March 23, 2013, In : Mineral of the Month

Nebula stone. To quote from the Nebula Stone website: “There are companies that are trying to capitalize on the popularity of our stone’s name (Nebula Stone) because they have learned it has become very popular around the World. Some unethical companies have intentionally sold Kambaba/Kambamba/Kabamba Jasper/Crocodile rock/Galaxyite from Madagascar and South Africa falsely calling them Nebula Stone. Kambaba Jasper is not Nebula Stone. Nebula Stone is an igneous stone (from within the Eart...
Continue reading ...

Jaspers Galore

Posted by Site Moderator Webmaster on Saturday, March 23, 2013, In : Mineral of the Month

JASPER – THE HISTORY

The name jasper means "spotted or speckled stone", and is derived via Old French jaspre (variant of Anglo-Norman jaspe) and Latin iaspidem (nom. iaspis)) from Greek ἴασπις iaspis, (feminine noun) from a Semitic language (cf. Hebrew יושפה yushphah, Akkadian yashupu).

Green jasper was used to make bow drills in Mehrgarh between 4th and 5th millennium BC. Jasper is known to have been a favourite gem in the ancient world; its name can be traced back in Arabic, P...
Continue reading ...

Mineral of the Month - Ruby Corundum

Posted by Site Moderator Webmaster on Wednesday, November 21, 2012, In : Mineral of the Month

Ruby from Afghanistan Ruby from Musina, S.A.

Specimen size 2,7 cm x 1,2 cm Specimen 2,5 cm, crystal 0,5 cm

Macro of Ruby corundum from Poona ...

Mineral of the Month - Quartz

Posted by Site Moderator Webmaster on Thursday, October 25, 2012, In : Mineral of the Month

We all think we know quartz, and can recognise it, but it has possibly greater variation than any other mineral. First, it is only one of several different silica minerals made of only silicon and oxygen, linked together in the proportions of two oxygen atoms per silicon atom, hence the chemical formula SiO2. The other minerals, with identical chemical composition are tridymite and cristobalite (both high temperature minerals) and coesite and stishovite (both high pressure minerals). There is...
Continue reading ...

Mineral of the Month - Braunite

Posted by Site Moderator Webmaster on Monday, September 24, 2012, In : Mineral of the Month

    Braunite II, andradite garnet, ettringite                          Braunite II on andradite garnet
                       (Wessels mine)                             (Wessels mine
      Braunite II crystal (2,7 cm x 1,4 cm)                             specimen (4,1 cm x 3,5 cm)

Crystal system:        Tetragonal        Hardness:        6-6,5

Density:        4.8            Streak:            Black

Cleavage:        Perfect            Composition:        silicate    Mn...
Continue reading ...

SPODUMENE

Posted by Site Moderator Webmaster on Friday, July 20, 2012, In : Mineral of the Month

Crystal system: monoclinic Hardness: 6,5 - 7

Density: 3,2 Streak: White
Cleavage: Perfect Composition: silicate LiAlSi2O6

Spodumene is derived from the Greek word “spodoumenos”, which translates to “burnt to ash”, which refers to the ashy colour of early specimens. Spodumene is a relatively new mineral having been discovered in the last 300 years, and gem varieties have only been discovered in the last ...
Continue reading ...

Anorthoclase Crystal, Mount Erebus, Antarctica

Posted by Site Moderator Webmaster on Monday, June 25, 2012, In : Mineral of the Month

Mount Erebus, the second highest volcano in Antarctica with a summit elevation of 3,794 metres, is located on Ross Island, which is also home to three inactive volcanoes. Mount Erebus is part of the Pacific Ring of Fire, which includes over 160 active volcanoes.

Geology and Volcanology
The mineral anorthoclase ((Na,K)AlSi3O8) is a crystalline solid solution in the alkali feldspar series, in which the sodium-aluminium silicate member exists in larger proportion. It typically consists of between ...
Continue reading ...

Mineral of the Month - Opal

Posted by Site Moderator Webmaster on Wednesday, April 18, 2012, In : Mineral of the Month

Common or potch opal, 6cm x 4cm Locality unknown
Opalised ammonite, 6,5 cm x 4,5 cm Madagascar

Crystal system:                Amorphous
Hardness:                        4,5 – 6,5
Density:                           1.9 – 2.3
Streak:                            White
Cleavage:                         None
Composition:  ...

Mineral of the Month - Pink Diamond

Posted by Site Moderator Webmaster on Thursday, March 22, 2012, In : Mineral of the Month

An Australian mining company says it has found a 12,76 carat pink diamond, the largest rough pink diamond found in the country. The rare diamond was found at Rio Tinto's Argyle diamond mine in Western Australia's East Kimberly region. Estimated to be worth millions, it has been named the Argyle Pink Jubilee, and is being cut and polished in Perth. It will be sold later this year after being shown around the world, including in New York and...

Mineral of the month - Coronadite

Posted by Site Moderator Webmaster on Sunday, February 19, 2012, In : Mineral of the Month

We are pleased to inform you that the mineral coronadite has just been identified at the Rosh Pinah Zinc Mine for the first time.

It is a predominantly lead based mineral with the formula Pb (Mn^4+, Mn³⁺)8O16. It is monoclinic, with a hardness of 4½-5, and a member of the Cryptomelane Group. Its morphology is massive, with boytroidal crusts with a fibrous structure. It was first identified as a mineral in 1904, and is named after Francisco Vasquez de Coronado (ca. 1500-1554), the first Sp...

Fruits of the earth - Opal Pineapples

Posted by Site Moderator Webmaster on Sunday, January 15, 2012, In : Mineral of the Month

There are some mineral specimens in this world that beggar belief and the opal pineapples from White Cliffs in Australia are amongst those. They are palm-sized clusters of radiating points, looking like some bizarre fruit and have been known since the beginning of the 20^th century. Found only in the Cretaceous sediments of the White Cliffs opal field in New South Wales, they occurred in an area which has also produced opalised fossils of marine shells, pieces of wood, and even the occasional ...

Mineral of the Month - ZINC ORES – SPHALERITE

Posted by Site Moderator Webmaster on Friday, October 21, 2011, In : Mineral of the Month

The main ore types mined at Rosh Pinah are carbonate ore, microquartzite ore, and arkose ore containing mainly the sulphide ore minerals sphalerite (ZnS), galena (PbS), chalcopyrite (CuFeS2) and Pyrite (FeS). Specimen grade sphalerite crystals are occasionally found as attractive dark brown metallic euhedral cubes in vugs and quartz veins in this mine.

Photo. G Hinder

They can also occur as an adamantine lustre of golden brown and even yellow green colour, but not at Rosh Pinah. These crysta...

Mineral of the Month - Jeremejevite

Posted by Site Moderator Webmaster on Wednesday, September 28, 2011, In : Mineral of the Month

Crystal system: Hexagonal Hardness: 6,5 – 7,5

Density: 3,28 – 3,31 Streak: White

Colour: Colourless, white, yellowish, pale to dark blue

Cleavage: None

Occurrence: A rare late hydrothermal mineral formed in granitic pegmatites.

Habitat: ...

Mineral of the Month - Chrysoberyl

Posted by Site Moderator Webmaster on Sunday, August 28, 2011, In : Mineral of the Month

Crystal system: Orthorhombic Hardness: 8,5

Density: 3,5 – 3,84 Streak: White

Colour: Various shades of green, yellow, brownish to green black (can be raspberry-red under incandescent light when chromium is present)

Cleavage: Distinct, imperfect

Occurrence: ...

Mineral of the Month - Stilbite

Posted by Site Moderator Webmaster on Saturday, July 23, 2011, In : Mineral of the Month

NaCa₂Al₅Si₁₃O₃₆ 14H₂O, Hydrated sodium calcium aluminum silicate

At one time heulandite and stilbite were considered to be identical minerals. After they were found to be two separate species, in 1818, the name desmine ("a bundle") was proposed for stilbite, and this name is still employed in Germany. The English name "stilbite" is from the Greek stilbein = to shine, because of the pearly luster of the {010} faces.

Stilbite is a common and perhaps the most popular zeolite mineral ...

Mineral of the Month - Analcime

Posted by Site Moderator Webmaster on Friday, June 24, 2011, In : Mineral of the Month

Goboboseb crystals showing crystal clear analcime – photos and specimens PdB

NaAlSi2O6-H2O, Hydrated Sodium Aluminium Silicate

The name of the mineral comes from the Greek word analkis that means weak.

Analcime is a zeolite and occurs frequently in basalts and other basic igneous rocks associated with other Zeolites.

Crystal system: triclinic (Pseudo-cubic)

The aluminosilicate framework of the crystal structure does not change in topology at all. The reduction...

Mineral of the Month - Cuprite

Posted by Site Moderator Webmaster on Friday, June 24, 2011, In : Mineral of the Month

Crystal system: Isometric Hardness: 3,5 - 4,0

Density: 6,15 average Streak: Red

Colour: Red to a deep red that can appear almost black.

Cleavage: Is fair in four directions forming octahedrons.

Occurrence: Oxidized zone of co...

Mineral of the Month - Galena

Posted by Site Moderator Webmaster on Monday, April 25, 2011, In : Mineral of the Month

Crystal system: Isometric Hardness: 2.5 – 3.0

Density: 7.5 average Streak: Lead-grey

Colour: Silver lead-grey

Cleavage: Perfect, parallel to the faces of the cubic crystals

Occurrence: In vein deposits and irregular pockets w...

Mineral of the Month - Kutnohorite

Posted by Site Moderator Webmaster on Saturday, March 26, 2011, In : Mineral of the Month

Kutnohorite from Wessels and N’Chwanning mines (KMF). Specimens and photos by – J de Jongh

Crystal system: Trigonal Hardness: 3.5 - 4

Density: 3.11 average Cleavage: perfect

Streak: white

Colour: white, light brown, light yellow, light...

Mineral of the Month - Barite

Posted by Site Moderator Webmaster on Tuesday, February 22, 2011, In : Mineral of the Month

Barite from Rosh Pinah, Namibia. ± 20 cm X 13 cm X 13 cm Specimen and photos – J de Jongh

Crystal system: Orthorhombic Hardness: 2,5 - 3,5

Density: 4.5 average Cleavage: very good

Streak: white

Colour: Colourless, white, blue, red, yellow, o...

Mineral of the Month - Cerussite

Posted by Site Moderator Webmaster on Thursday, January 27, 2011, In : Mineral of the Month

Crystal system: Orthorhombic Hardness: 3 - 3,5

Density: 6,5 average Cleavage: good

Streak: white Colour: colourless. white, gray, blue, and green

Colour:

Occurrence: Occurrence: It is a lead carbonate mineral, usually found in the oxidized zones of lead ore deposits. It is a ...

Mineral of the Month - Sphene or Titanite

Posted by Site Moderator Webmaster on Friday, November 26, 2010, In : Mineral of the Month

Top lustre multicolour sphene        Yellow-green VS Sphene         Bright, neon-green Sphene crystal
www.aquarist-classifieds.co.uk       www.aquarist-classifieds.co.uk        very gemmy with good lustre,
                                                                                                                from Tanzania 62 carats, 3.5 x 2.5 x 0.9 cm
                                                                                                                www.marinmin...
Continue reading ...

Mineral of the Month - Azurite

Posted by Site Moderator Webmaster on Tuesday, October 26, 2010, In : Mineral of the Month

Azurite from Tsumeb, Namibia. Specimen and photo – J de Jongh

Crystal system: Monoclinic Hardness: 3,5 - 4

Density: 3.83 average Cleavage: perfect

Streak: light blue Colour: blue to very dark blue.

Occurrence: A secondary mineral found in the oxidized zones of copper-bearing ore depo...

Mineral of the Month - Mimetite

Posted by Site Moderator Webmaster on Thursday, September 23, 2010, In : Mineral of the Month

Mimetite from Tsumeb, Namibia. Specimens and photo by – J de Jongh

Crystal system: Hexagonal Hardness: 3,5 - 4

Density: 7,1 – 7,24 Cleavage: Imperfect

Streak: White Colour: White, yellow, orange, brown, red.

Occurrence: A secondary mineral found in the oxidized zones of...

Mineral of the Month - Schorl

Posted by Site Moderator Webmaster on Friday, August 27, 2010, In : Mineral of the Month

SCHORL (TOURMALINE GROUP)

Schorl from Erongo, Namibia. Specimens and photo – J de Jongh

Crystal system: trigonal Hardness: 7

Density: 3.1 - 3.25 Cleavage: None

Streak: white

Colour: black, brownish ...

Mineral of the Month - Orbicular Granite

Posted by Site Moderator Webmaster on Friday, July 23, 2010, In : Mineral of the Month

Along with several other club members, TVJ has always been curious about the strange formation of orbicular granite. He challenged Nick Norman as to whether there was any information about this granite in his book Geological Journeys, when Nick was at the club in July. Yes, there was, and this is what it says: “have a look at the famous, rare orbicular granite west of the village of Concordia. It’s a national monument, and one of just two known occurrences in South Africa, and of only a h...

Mineral of the Month - Diamond

Posted by Site Moderator Webmaster on Monday, June 28, 2010, In : Mineral of the Month

What is it that makes a diamond so attractive, and probably more sought after than any other gem? It is very hard and durable; yes, being 10 on the Mohs scale. It facets beautifully, and has industrial uses as well simply featuring in the jewellery trade. Diamonds can also be found in a variety of colours, including black, brown, yellow, with pale blue, and then red, green, and even pure orange and violet, which are the most rare. Formed up to 150 km under the ground, millions of diamonds...
Continue reading ...

Mineral of the Month - Hausmannite

Posted by Site Moderator Webmaster on Monday, May 24, 2010, In : Mineral of the Month

Crystal system:             Tetragonal                               Hardness:          5.5

Density:                        4.7 - 4.84                                  Cleavage:         Perfect

Streak:                          Brown                                       Colour:             Black metallic

Occurrence: Occurs mainly in high temperature hydrothermal veins and in contact metamorphic deposits.

Habitat: Crystals are pseudo octahedral up to 7,5 cm.    Composition:    Mn2+ Mn3+2 O4

Followi...
Continue reading ...

Mineral of the Month - Vanadinite

Posted by Site Moderator Webmaster on Tuesday, May 11, 2010, In : 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 eventua...
Continue reading ...

Mineral of the Month – Epidote

Posted by Site Moderator Webmaster on Tuesday, May 11, 2010, In : Mineral of the Month

Epidote is a hydrous calcium iron alumino-silicate of medium hardness, between 6 and 7 on Mohs’s scale, and found in distinctive yellowish-green (“pistachio”) tones that range to an almost black colour. It is a metamorphic mineral, named by Hauy in 1801 from a Greek word “epidosis” meaning “addition”, because it was found to be an additional new mineral, and not a variety of tourmaline which it sometimes resembles, and until then what it was thought to be. Its crystals are rath...
Continue reading ...

Articles

Showing category "Mineral of the Month" (Show all posts)

MINERAL OF THE MONTH – OLIVINE

New Barite Occurrence at Rosh Pinah Mine – Namibia

A Bit about Blue Lace Chalcedony

Skorpion Zinc mine – another new mineral discovered

The Colours of Quartz

Jaspers - part 2

Jaspers Galore

Mineral of the Month - Ruby Corundum

Mineral of the Month - Quartz

Mineral of the Month - Braunite

SPODUMENE

Anorthoclase Crystal, Mount Erebus, Antarctica

Mineral of the Month - Opal

Mineral of the Month - Pink Diamond

Mineral of the month - Coronadite

Fruits of the earth - Opal Pineapples

Mineral of the Month - ZINC ORES – SPHALERITE

Mineral of the Month - Jeremejevite

Mineral of the Month - Chrysoberyl

Mineral of the Month - Stilbite

Mineral of the Month - Analcime

Mineral of the Month - Cuprite

Mineral of the Month - Galena

Mineral of the Month - Kutnohorite

Mineral of the Month - Barite

Mineral of the Month - Cerussite

Mineral of the Month - Sphene or Titanite

Mineral of the Month - Azurite

Mineral of the Month - Mimetite

Mineral of the Month - Schorl

Mineral of the Month - Orbicular Granite

Mineral of the Month - Diamond

Mineral of the Month - Hausmannite

Mineral of the Month - Vanadinite

Mineral of the Month – Epidote

Categories

Blog Archive