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9 Apr 2024: Magnetite. Title. Magnetite. Subject. Magnetite is the most abundant oxide in igneous rock. ... Silver-black. Metallic lustre. No cleavage. Rock Specimens. Mineral Name. magnetite. iron oxide.

9 Apr 2024: Relief: high. Isotropic. Mineral Specimens. M501 Magnetite. Brazil. Crystals showing the characteristic octahedral form. ... Silver-black. Metallic lustre. No cleavage. Rock Specimens. Mineral Name. magnetite. iron oxide.

9 Apr 2024: Alteration. Zonation. Accessory minerals:. - Sphene. - Magnetite. - Apatite. Rock History.

9 Apr 2024: Browse Items (264 total). Page. of 27. Sort by:. Formula NaCl Structure Non-silicate Crystal System Crystal system: cubic Physical Properties Colour in hand specimen: colourless or white when pure, more typically orange or red due to inclusions of

9 Apr 2024: Minerals. Rocks comprise minerals. In order to understand the paragenesis of a rock, be it igneous, sedimentary or metamorphic, we must identify its constituent minerals. The aim of this collection is to detail the structural, physical and optical

9 Apr 2024: Browse Items (7 total). Tags: igneous. Sort by:. Formula Ca5(PO4)3(OH,F,Cl) Structure Non-silicate Crystal System Crystal system: hexagonal (-) Physical Properties Colour in hand specimen: green, white, yellow, blue brown etc.Hardness: 5 Optical

9 Apr 2024: The olivine has decomposed to magnetite and serpentine. Relict olivine grains display characteristic curving cracks andClinopyroxene (augite). - ... Some simple twinning. Accessory minerals. - Opaque, interstitial, probably magnetite. Rock History.

9 Apr 2024: Some areof magnetite, clinopyroxene and other minerals. Extensive alteration along abundant cracks. ... Groundmass. - Fine-grained. Plagioclase feldspar needles, clinopyroxene, some olivine (mostly altered), and opaques, probably magnetite.

9 Apr 2024: The olivine has decomposed to magnetite and serpentine. Relict olivine grains display characteristic curving cracks andClinopyroxene (augite). - ... Some simple twinning. Accessory minerals. - Opaque, interstitial, probably magnetite. Rock History.

9 Apr 2024: Bottryoidal hematite crystal. Hematite crystal strucutre, CrystalMaker. Formula. Fe. 2. O. 3. Structure. Non-silicate. Crystal System. Crystal system: trigonal (-). Physical Properties. Colour in hand specimen: black, steel-grey and bright to dull

9 Apr 2024: Mica, biotite. hand specimen of biotite mica. Crystals of bioitie mica with perfect basal cleavage. Biotite sheet silicate crystal structure, CrystalMaker. Formula. K. 2. (Mg,Fe. 2+. ). 6-4. (Fe. 3+. ,Al,Ti). 0-2. [Si. 6-5. Al. 2-3. O. 20. ](OH,F).

9 Apr 2024: Some areof magnetite, clinopyroxene and other minerals. Extensive alteration along abundant cracks. ... Groundmass. - Fine-grained. Plagioclase feldspar needles, clinopyroxene, some olivine (mostly altered), and opaques, probably magnetite.

9 Apr 2024: Strongly pleochroic in reddish brown and pale straw. Often associated with small grains of an opaque accessory mineral, probably magnetite.

9 Apr 2024: Alteration to magnetite and serpentine, particularly along the curving cracks. Cracks across the thin-section, could be due to expansion of the rock as the olivine was altered.

9 Apr 2024: Halite cubic crystal structure with large Cl. -. anions (green) and small Na. cations (yellow). This mineral is commonly known as rock salt. Formula. NaCl. Structure. Non-silicate. Crystal System. Crystal system: cubic. Physical Properties. Colour

9 Apr 2024: Sphene crystal structure, CrystalMaker. Formula. CaTi[SiO. 4. ](O, OH, F). Structure. Orthosilicate. Crystal System. Crystal system: monoclinic (). Physical Properties. Colour in hand specimen: colourless, yellow, green, brown or black. Cleavage: one

9 Apr 2024: Gypsum single crystal hand specimen, monoclinic symmetry apparent. Milky, opaque gypsum with twinned crystal habit. Gypsum crystal structure showing monoclinic symmetry, CrystalMaker. Formula. CaSO. 4. 2H. 2. 0. Structure. Non-silicate. Crystal

9 Apr 2024: Galena crystal structure, with large yellow sulfur and small purple lead symbols. Galena in hand specimen. Formula. PbS. Structure. Non-silicate. Crystal System. Crystal system: cubic. Physical Properties. Colour in hand specimen: lead grey. Streak:

9 Apr 2024: Zircon crystal structure (tetragonal), CrystalMaker. Zircon is a common accessory mineral of many igneous rocks. Pleochroic haloes are formed by damage to the crystal lattice of enclosing minerals by the radioactive decay of elements such as Th and

9 Apr 2024: Epidote crystal structure. Formula. Ca. 2. Al. 2. O(Al,Fe. 3+. )OH[Si. 2. O. 7. ][SiO. 4. ]. Structure. Orthosilicate. Crystal System. Crystal system: monoclinic (-). Physical Properties. Colour in hand specimen: green. Cleavage: one, perfect.

9 Apr 2024: Apatite crystal structure, CrystalMaker. Formula. Ca. 5. (PO. 4. ). 3. (OH,F,Cl). Structure. Non-silicate. Crystal System. Crystal system: hexagonal (-). Physical Properties. Colour in hand specimen: green, white, yellow, blue brown etc. Hardness: 5.

9 Apr 2024: Garnet (euhedral) in hand specimen. Formula. (Mg,Fe,Ca). 3. Al. 2. Si. 3. O. 12. Structure. Orthosilicate. Crystal System. Crystal system: cubic. Physical Properties. Colour in hand specimen: typically red. Cleavage: none. Hardness: 6-7.5. Optical

9 Apr 2024: Pyrite crystals, with metallic lustre. Pyrite crystals within quartz. Pyrite cubis crystal structure, showing octahedral coordination of Fe by S. Formula. FeS. 2. Structure. Non-silicate. Crystal System. Crystal system: cubic. Physical Properties.

9 Apr 2024: Alteration. Zonation. Accessory minerals:. - Sphene. - Magnetite. - Apatite. Rock History.

9 Apr 2024: Alteration to magnetite and serpentine, particularly along the curving cracks. Cracks across the thin-section, could be due to expansion of the rock as the olivine was altered.

9 Apr 2024: Olivine hand specimen, no cleavage. Olivine crystal structure, CrystalMaker. Formula. (Mg,Fe). 2. [SiO. 4. ]. Structure. Orthosilicate. Crystal System. Crystal system: orthorhombic () (-). Physical Properties. Colour in hand specimen: pale green.

9 Apr 2024: Quartz single crystal, no cleavage, conchoidal fracture. Quartz prisms, vitreous lustre. Quartz prisms (roughly hexagonal habit). Quartz crystal structure (trigonal unit cell), CrystalMaker. Formula. SiO. 2. Structure. Framework silicate. Crystal

9 Apr 2024: Chlorite crystal structure, CrystalMaker. Formula. (Mg,Fe. 2+. ,Fe. 3+. ,Mn,Al). 12. [(Si,Al). 8. O. 20. ](OH). 16. Structure. Sheet silicate. Crystal System. Crystal system: monoclinic () (-). Physical Properties. Colour in hand specimen: green.

9 Apr 2024: Fluorite crystal hand specimen, purple hue. Fluorite crystal structure (cubic), CrystalMaker. Formula. CaF. 2. Structure. Non-silicate. Crystal System. Crystal system: cubic. Physical Properties. Colour in hand specimen: extremely variable:

9 Apr 2024: Anhydrite crystal structure, CrystalMaker. Formula. CaSO. 4. Structure. Non-silicate. Crystal System. Crystal system: orthorhombic (). Physical Properties. Colour in hand specimen: white or colourless when pure. Cleavage: two at 90. Hardness: 3-3.5.

9 Apr 2024: Single crystal calcite hand specimen. Small calcite crystals growing from a free surface. Milky single crystal of calcite. Calcite crystal structure, CrystalMaker. Formula. CaCO. 3. Structure. Non-silicate. Crystal System. Crystal system: trigonal (-

9 Apr 2024: Dolomite in hand specimen. Dolomite crystal structure, CrystalMaker. Formula. CaMg(CO. 3. ). 2. Structure. Non-silicate. Crystal System. Crystal system: trigonal (-). Physical Properties. Colour in hand specimen: white, often tinged with yellow or

9 Apr 2024: Mica, muscovite. Crystals of muscovite with basal cleavage. Crystals of muscovite, colourless. Muscovite crystal structure (a sheet silicate), CrystalMaker. Formula. K. 2. Al. 4. [Si. 6. Al. 2. O. 20. ](OH,F). 4. Structure. Sheet silicate. Crystal

9 Apr 2024: Serpentine crystal lattice, with sheet silicate structure (CrystalMaker). Serpentine is a common alteration product of olivine, produced by hydration at low temperatures. Formula. Mg. 3. [Si. 2. O. 5. ](OH). 4. Structure. Sheet silicate. Crystal

9 Apr 2024: Tourmaline crystal structure (trigonal), CrystalMaker. Tourmaline is the only common mineral of which boron is an essential constituent. Its presence in a rock, therefore, indicates that the rock contains significant boron. Formula.

9 Apr 2024: Amphibole (hornblende). Amphibole hand specimen. Amphibole hand specimen. Formula. (Na,K). 0-1. Ca. 2. (Mg,Fe. 2+. ,Fe. 3+. ,Al). 5. Si. 6-7.5. Al. 2-0.5. O. 22. (OH). 2. Structure. Chain silicate. Crystal System. Crystal system: monoclinic () (-).

9 Apr 2024: Orthopyroxene. Orthopyroxene crystal structure, CrystalMaker. Orthopyroxene chemical variability. Enstatite (common in mafic rocks) always has high Mg and low Ca. Formula. (Mg,Fe). 2. Si. 2. O. 6. Structure. Chain silicate. Crystal System. Crystal

9 Apr 2024: Plagioclase feldspar. Plagioclase feldspar hand specimen, polycrystalline with opaque, white colour. Plagioclase feldspar with optical schiller. Plagioclase feldspar crystal structure, CrystalMaker. Formula. Na[AlSi. 3. O. 8. ] – Ca[Al. 2. Si. 2.

9 Apr 2024: Strongly pleochroic in reddish brown and pale straw. Often associated with small grains of an opaque accessory mineral, probably magnetite.

9 Apr 2024: Alkali Feldspar. Alkali feldspar hand specimen, pink hue. Alkali feldspar hand specimen, milky white. Simply twinned alkali feldspar in granite. Alkali feldspar unit cell, CrystalMaker. Formula. (K,Na)[AlSi. 3. O. 8. ]. Structure. Framework

9 Apr 2024: Clinopyroxene (augite). Phase diagram deomstrating the chemical compositional range for clinopyroxenes. Formula. (Ca,Mg,Fe. 2+. ,Fe. 3+. ,Ti,Al). 2. [(Si,Al). 2. O. 6. ]. Structure. Chain silicate. Crystal System. Crystal system: monoclinic ().

9 Apr 2024: Browse Items (264 total). Page. of 27. Sort by:. Compare with phenocryst. Formula Fe3O4 Structure Non-silicate Crystal System Crystal system: cubic Physical Properties Colour in hand specimen: blackStreak: blackCleavage: noneHardness: 7.5-8 Optical

9 Apr 2024: Browse Items (264 total). Page. of 27. Sort by:. Formula (K,Na)[AlSi3O8] Structure Framework silicate Crystal System Crystal system: monoclinic (-) or triclinic () (-) Physical Properties Colour in hand specimen: white or pink Cleavage: two at 90

9 Apr 2024: Browse Items (264 total). Page. of 27. Sort by:. Formula Fe3O4 Structure Non-silicate Crystal System Crystal system: cubic Physical Properties Colour in hand specimen: blackStreak: blackCleavage: noneHardness: 7.5-8 Optical Properties Colour in

9 Apr 2024: Browse Items (7 total). Tags: igneous. Sort by:. Formula (Na,K)0-1Ca2(Mg,Fe2+,Fe3+,Al)5Si6-7.5Al2-0.5O22(OH)2 Structure Chain silicate Crystal System Crystal system: monoclinic () (-) Physical Properties Colour in hand specimen: black Cleavage:

9 Apr 2024: Browse Items (7 total). Tags: igneous. Sort by:. Formula (Na,K)0-1Ca2(Mg,Fe2+,Fe3+,Al)5Si6-7.5Al2-0.5O22(OH)2 Structure Chain silicate Crystal System Crystal system: monoclinic () (-) Physical Properties Colour in hand specimen: black Cleavage:

9 Apr 2024: Browse Items (7 total). Tags: igneous. Sort by:. Formula SiO2 Structure Framework silicate Crystal System Crystal system: trigonal () Physical Properties Colour in hand specimen: colourless Lustre: vitreous Pleochroism: none Cleavage: