Silicate Mineral Collection (page 2)

Imperial Topaz
Found in 1852 in one of the oldest mines in the southeastern Ouro Preto region of Brazil

Moss agate specimen

Agate

Bloodstone or heliotrope carvings
These frogs were carved from bloodstone by Paul Dreher. Bloodstone is green agate containing speckles of red jasper. All these derive from the cryptocrystalline quartz group

Crystal balls are produced by grinding and polishing quartz (silicon dyoxide) cystal into spheres

Cordierite-biotite-gneiss
Geological specimen collected by Scotts British Antarctic Expedition 1910-1913, also known as the Terra Nova expedition. It had a broad scientific programme and collected thousands of geological

Agate
Blue lace agate

Cursed amethyst
When the Mineralogy Department received this amethyst in 1943 they found a note inside the box: this stone is trebly accursed and is stained with the blood

Antigorite and bowenite
Group of two specimens of antigorite (above) and two specimens of antigorite var. bowenite below. Both these specimens comprise of (magnesium iron silicate hydroxide)

The Esquel pallasite

Plate 10, fig 1 from Mineralienbuch
An illustration of an axinite mineral specimen. Plate 10, fig 1 from Mineralienbuch by F. A. Schmidt, Stuttgart 1855

Plate 3, fig 4 from Mineralienbuch
A illustration of a slice of polished brown jasper. Jasper is a variety of cryptocrystalline quartz (silicon dioxide). Plate 3, fig 4 from Mineralienbuch by F. A. Schmidt, Stuttgart 1855

Plate 10, fig 2 from Mineralienbuch
An illustration of an andalusite mineral deposit showing columnar crystals. Plate 10, fig 2 from Mineralienbuch by F. A. Schmidt, Stuttgart 1855

Agate
This polished agate specimen from Saxony is called Breccia Sanguigna. This brecciated agate comprises mainly of irregular sized fragments of cryptocrystalline quartz, set in a finer matrix

Agate
A polished slice of agate from Uraguay. Agate (silicon dioxide) is a cryptocrystalline quartz

Chrome diopside
Two variations of a diopside gemstone (calcium magnesium silicate). Left: Deep-green faceted cut stone; locality unknown. Right: Small translucent green detached crystal from Outokumpu, Finland

Plate 53 from Mineralogie
Mine de Plomb blanc en rayon et Colore du Hars tire du Cabinet de Mr. Aubert. From Recuille complet de Mineralogie? vol.6 (1790) by F.L. Swebach Desfontaines

Agate
A polished slice of agate or chalcedony from Uraguay. Agate (silicon dioxide) is a cryptocrystalline quartz

Plate 102 from Mineralogie
Superbe groupe de grands cristaux d Aigue marine de Siberie. From Recuille complet de Mineralogie Vol.3 (1790) by F. L. Swebach Desfontaines

Jadarite specimen
The mineral jadarite has the same chemical composition as kryptonite. Discovered in Serbia in 2006, jadarite is composed of sodium, lithium, boron silicate and hydroxide

Birthstone Series: Zircon
Zircon comes in a variety of colours, but most commonly brown or green. It is the birthstone for the month of December (along with Tanzinte and Turquoise). Photographed by Harry Taylor

Birthstone Series: Lazurite

Birthstone Series: Citrine
Citrine is a form of quartz that appears in different a variety of yellows and oranges, it is the birthstone for the month of November along with Topaz. Specimen number 21470

Included diamond gemstone
A two-carat rectangular step-cut diamond with a large violet-red garnet inclusion visible in the table facet

Sapphire turban button
A rose-cut facetted deep-blue sapphire mounted in a button of quartz, inlaid with gold, rubies & emeralds. No 198 in the collection of Sir Hans Sloane

Uvarovite garnets comprise of (calcium chromium silicate). They are characterized by their green colour and rounded crystals of either 12 or 24 faces

Gobbinsite comprises of (hydrated sodium potassium calcium aluminum silicate) and derives from the zeolite group. Specimen found nr. Black Cave, Island Magee, Co. Antrim

Orthoclase (potassium aluminum silicate) is a major granite forming mineral. Specimen from Brevik, Norway

Rhodonite
A pink specimen of rhodonite (manganese iron magnesium calcium silicate). Rhodon is greek for rose. Specimen from the Natural History Museum, London

Spessartine comprises of (manganese aluminum silicate) and is found in metamorphic environments

Phenakite is comprised of (beryllium silicate). Visually it closely resembles quartz, but chemically it is closer to gemstones such as topaz and beryl

Tanzanite crystal and cut stone
This is a blue variety of the mineral zoisite. Strongly pleochroic, it displays rich blue, magenta and yellowish-grey colours when viewed from different angles

Topaz comprises of (aluminum silicate fluoride hydroxide). This is a specimen from the collections of the Natural History Museum, London

Amethyst crystals

Russian topaz
Topaz comprises of (aluminum silicate fluoride hydroxide) and is the birthstone of November. Brown topaz specimens from the collections of the Natural History Museum, London

Lazurite comprises of (sodium calcium aluminum silicate sulphur sulphate). Due to its unique rich colour, it is a semi-precious stone and is often used in jewellery making

Cassiterite pseudomorphous after orthoclase
Brown granular cassiterite (tin oxide) have replaced twinned orthoclase crystals. Wheal Coates, St. Agnes, Cornwall

Zircon is the birthstone of December. It comprises of (zirconium silicate) and is not the same as the artificial gem cubic zircona. Crystal specimens are from Nigeria

Carved carnelian bowl
Carnelian is a transluscent yellow to orange variety of chalcedony (micro-crystalline quartz). This bowl was once the property of Sir Hans Sloane

Kyanite comprises of (aluminum silicate) and shares this composition with both sillimanite and adalusite. Specimen from the Natural History Museum, London

Spessartine garnet
Spessartine comprises of (manganese aluminum silicate). A cut stone and crystal from the collections of the Natural History Museum, London

Rubellite (Tourmaline) decoratively carved pendant. Specimen from the collections of the Natural History Museum, London

Birthstone Series: Emerald
A specimen of the gemstone, emerald from the Natural History Museum, London. Emerald is the birthstone for the month of May (along with Chrysoprase). Photographed by Harry Taylor

Birthstone Series: Carnelion
A specimen of the mineral, carnelion (BM58673a) from the Natural History Museum, London. Carnelion is the birthstone for the month of July (along with Ruby). Photographed by Harry Taylor

Pleochroism in an iolite cut stone
This iolite (magnesium aluminium silicate) is displaying pleochroism, a varied colour effect as the gem is turned. See also 3960

Mocha stone, sardonyx and agate
Mocha stone and sardonyx cameos resting on artificially dyed slabs of agate. All these varieties of chalcedony derive from the cryptocrystalline quartz group

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