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Minerals

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Magnesio-foitite tourmaline from Madagascar. A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are over 5500 named and described minerals - about 200 of them are common and about 20 of them are very common. Mineral classification is based on anion chemistry. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates. The silicates are the most abundant and chemically complex group of minerals. All silicates have silica as the basis for their chemistry. "Silica" refers to SiO2 chemistry. The fundamental molecular unit of silica is one small silicon atom surrounded by four large oxygen atoms in the shape of a triangular pyramid - this is the silica tetrahedron - SiO4. Each oxygen atom is shared by two silicon atoms, so only half of the four oxygens "belong" to each silicon. The resulting formula for silica is thus SiO2, not SiO4. Tourmaline is a classic "garbage-can mineral" - it has a little bit of just about everything. Tourmaline can be given the formula (Na,Ca)(Li,Mg,Al)(Fe,Mn,Al)6(BO3)3(Si6O18)(OH,F)4 - sodium calcium lithium magnesium iron manganese hydroxy-fluoro-boro-aluminosilicate. Tourmaline has a nonmetallic luster, varies in color but is often blackish, has a white streak, is quite hard (H = 7 to 7.5), frequently has elongated crystals with rounded triangular cross-sections and striated faces, no cleavage, and conchoidal fracture. Tourmaline is a group of minerals, the most common of which is the blackish-colored, Fe-rich schorl (see elsewhere in this photo album). Dark brown, Mg-rich dravite is another moderately common variety of tourmaline. Other varieties include achroite, elbaite (Li & Na-rich), indicolite, liddicoatite (Li & Ca-rich), rubellite, verdelite, and others. The latter-listed tourmalines are often richly colored (greenish, yellowish, reddish, pinkish, bluish, multicolored). Tourmaline is moderately common in pegmatites and some metamorphic rocks. It can even be rock-forming - see the scarce rock tourmalinite (<a href="https://www.flickr.com/photos/jsjgeology/15095512541">www.flickr.com/photos/jsjgeology/15095512541</a>). The crystal shown above is a scarce variety of tourmaline called magnesio-foitite (magnesiofoitite) - Na(Mg2Al)Al6(Si6O18)(BO3)3(OH)4 (= sodium magnesium hydroxy-boro-aluminosilicate). This specimen likely comes from a pegmatite. Locality: unrecorded locality attributed to Antananarivo Province, central Madagascar Photo gallery of tourmaline: <a href="http://www.mindat.org/gallery.php?min=4003" rel="noreferrer nofollow">www.mindat.org/gallery.php?min=4003</a> Mineral

Magnesio-Foitite

magnesio-foitite

Formula
(☐,Na)(Mg2Al)Al6(Si6O18)(BO3)3(OH)3(OH)
Mohs
7
Magnesiohastingsite from Bratislava, Slovakia. Specimen size 4.5 cm Mineral

Magnesio-Hastingsite

magnesio-hastingsite

Formula
NaCa2(Mg4Fe³⁺)(Si6Al2)O22(OH)2
Magnesio-hornblende from Burk's Falls highway roadcuts, Armour Township, Parry Sound District, Ontario, Canada. An impressive columnar cluster with striking opposing crystals of magnesio-hornblende crystals is perched on matrix on this aesthetic large specimen from the Robert Nowakowski Collection. The sharply terminated, highly lustrous jet-black parallel-growth crystals, to 6.0 cm, are starkly contrasted by the melted-look quartz crystals below. Mineral

Magnesio-Hornblende

magnesio-hornblende

Formula
☐Ca2(Mg4Al)(Si7Al)O22(OH)2
Mohs
5.5
Mineral

Magnesio-Lucchesiite

magnesio-lucchesiite

Formula
CaMg3Al6(Si6O18)(BO3)3(OH)3O
Colour
black
Quartz, Magnesioriebeckite Locality: Antequera, Málaga, Andalusia, Spain (Locality at mindat.org) Size: 8 x 5 x 3 cm. Definitely one of the finer specimens of the unusual and striking Blue Quartz from the famous locality in Spain. These modified crystals have good crystal development for the variety. Here, the best-developed crystal (.4 cm on edge) has a modified termination that almost looks dipyramidal, and the luster is superb. The blue color is caused by fibrous inclusions of Magnesioriebeckite. Mineral

Magnesio-Riebeckite

magnesio-riebeckite

Formula
☐Na2(Mg3Fe³⁺2)Si8O22(OH)2
Mohs
6
Mineral

Magnesioalterite

magnesioalterite

Formula
Mg2Fe³⁺4(SO4)4(C2O4)2(OH)4·17H2O
Sky blue crystals of the rare sulphate mineral magnesioaubertite from the type locality and only one of the two known localities worldwide: Faraglione Ranni, Vulcano Island, Lipari, Sicily, Italy. Mineral

Magnesioaubertite

magnesioaubertite

Formula
(Mg,Cu)Al(SO4)2Cl * 14H2O
Mineral

Magnesiobeltrandoite-2N3S

magnesiobeltrandoite-2N3S

Formula
(Mg6Al2)(Al18(Fe³⁺)2)O38(OH)2
Mineral

Magnesiobermanite

magnesiobermanite

Formula
MgMn³⁺2(PO4)2(OH)2*4H2O
Mineral

Magnesiocanutite

magnesiocanutite

Formula
NaMnMg2[AsO4]2[AsO2(OH)2]
Greenish single specimen of magnesiocarpholite from the TL in France (Vanoise, Savoie, Auvergne-Rhône-Alpes, France). Ex Vandenbroucke Museum collection from Waregem, Belgium. Mineral

Magnesiocarpholite

magnesiocarpholite

Formula
(Mg,Fe²⁺)Al2(Si2O6)(OH)4
Mineral

Magnesiochangesite-(Ce)

magnesiochangesite-(Ce)

Formula
(Ca8Ce)□Mg(PO4)7
Mineral

Magnesiochangesite-(Y)

magnesiochangesite-(Y)

Formula
(Ca8Y)◻Mg(PO4)7
Black sharp crystal of magnesiochloritoid from Austria (Hohe Tauern, Salzburg, Austria) in matrix. Ex Vandenbroucke Museum collection from Waregem, Belgium. Mineral

Magnesiochloritoid

magnesiochloritoid

Formula
MgAl2O(SiO4)(OH)2
Beige crystals of the extremely rare mineral magnesiochlorophoenicite from one of the only two known localities worldwide, the Sterling Hill mine (Sterling Hill, Ogdensburg, Sussex County, New Jersey, United States of America). Ex Vandenbroucke Museum collection from Waregem, Belgium. Mineral

Magnesiochlorophoenicite

magnesiochlorophoenicite

Formula
(Mg,Mn)3Zn2(AsO4)(OH,O)6
Magnesiochromite Locality: Mistake Mine (Butler Estate Mine; Mistaken; Big Ridge & Mistake Mine; James-Thickston; James-Thickstun Mine), Butler Estate Chrome deposit, Wright Mountain, New Idria District, Diablo Range, Fresno Co., California, USA A 3.2 by 2.5 cms mass of rough crystals. JSS specimen and photo Mineral

Magnesiochromite

magnesiochromite

Formula
MgCr³⁺2O4
Mohs
5.5
Yellow magnesiocopiapite crystals from United Verde Extension Mine, Jerome, Yavapai County, Arizona, United States of America. Ex Vandenbroucke Museum collection from Waregem, Belgium. Mineral

Magnesiocopiapite

magnesiocopiapite

Formula
MgFe³⁺4(SO4)6(OH)2 * 20H2O
Mineral

Magnesiocoulsonite

magnesiocoulsonite

Formula
MgV2O4
Mineral

Magnesiodumortierite

magnesiodumortierite

Formula
MgAl6BSi3O17(OH)
Magnesioferrite, black, grey, dark blue crystals with many faces, often with rounded sides, sometimes almost little balls. EDX showed: 45% Mg - 49% Fe - 5% Al - 1% Mn. Image width: 1,5mm - Locality: Wannenköpfe, Ochtendung, Eifel region, Germany Mineral

Magnesioferrite

magnesioferrite

Formula
MgFe³⁺2O4
Mineral

Magnesiofluckite

magnesiofluckite

Formula
CaMg(AsO3OH)2(H2O)2
Mineral

Magnesiohatertite

magnesiohatertite

Formula
(Na,Ca)2Ca(Mg,Fe³⁺)2(AsO4)3
Mineral

Magnesiohongruiite-(Fe³⁺)

magnesiohongruiite-(Fe³⁺)

Formula
(Mg2Fe³⁺)Fe³⁺NbO7(OH)
Brown acicular and platy crystals of the very rare borate magnesiohulsite from the type locality and only one of the three known localities worldwide (Qiliping Deposit, Changning County, Hengyang, Hunan Province, China). Ex Vandenbroucke Museum collection from Waregem, Belgium. Mineral

Magnesiohulsite

magnesiohulsite

Formula
Mg2Fe³⁺O2(BO3)