Garnet
Garnet from Lake Creek near the Heather Lake trail (west of Lake Wenatchee)
WHAT IS IT?
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A hard Silicate mineral having A 3B 2Si 3O 12, where X is a divalent cation (Fe 2+, Ca 2+, Mg 2+, Mn 2+) and Y is a trivalent cation (Fe 3+, Al 3+, Cr 3+)
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The birthstone for January
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The name comes from the Latin word “Garanatus”, meaning ”seedlike”, or like the seeds of a pomegranate.
HISTORY
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Used Since the Bronze Age
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A garnet bead necklace has been found in a 3000 BC grave
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Plato had his portrait engraved onto a garnet
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In Bohemia (part of the modern Czech Republic), castles and churches are decorated with Garnets
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Bohemian garnets are still used in traditional jewelry
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In medieval times, garnets were believed to cure depression
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Garnet is one Of the 12 gemstone on Aaron’s breastplate
WHAT TYPES ARE THERE?
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Colors: red, pink, orange, yellow, green, blue, brown, black. Red to reddish purple is the most common.
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There are different types that possess similar physical properties & crystalline form but different chemical compositions
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Garnets can be natural or synthetic
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The types form two groups, those with Aluminum in the Y site (Almandine, Pyrope, Spessartine) and those with Calcium in the B site (Andradite, Grossular, Uvarovite)
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Almandine -Fe₃Al₂Si₃O₁₂
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Gemstones of this type are a transparent deep red and are called “Carbuncle”. They occur in metamorphic rock such as mica schists.
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Andradite - Ca₃Fe₃₊ ₂Si₃O₁₂
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yellow, green, brown, or black in color Topazolite is yellow or green. Demantoid is green. Melanite is black. Demantoid called the "Emerald Of the Urals", is the most prized Of garnets
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Grossular - Ca₃Al₂Si₃O₁₂
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The name comes from the botanical name for gooseberry, grossularia, because of its often green coloring. Other varieties have red, yellow, or brown coloring.
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Pyrope - Mg₃Al₂Si₃O₁₂
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Deep red to black color. A variety known as rhodolite has a violet-red shade & is found in North Carolina. A more unusual type from Madagascar has a blue color that under LED lighting looks like a blue sapphire.
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Spessartine - Mn3Al2Si3O1
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Named after Spessart in Bavaria where it was found. Most commonly found in granite pegmatite. Orange-yellow varieties are found in Madagascar. Violet-red varieties are found in Colorado and Maine.
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Uvarovite - Ca3Cr2Si3O12
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A rare garnet having bright green coloring
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There are other less common species of garnet:
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Calcium in X site
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Hydroxide bearing with calcium in X site
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Magnesium or manganese in X site
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WHERE IS IT FOUND?
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The largest producers: Australia.
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Other producers: China. U.S.
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Collection sites in Washington State -
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Barclay Creek (Halford.WA)
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Buckhorn Mountain
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Deer Trail. Monitor Mine
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Denny Mountain (Snoqualmie pass) — Grossular garnet
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Garnet Creek (Barlow Pass)
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Gaynor (Snoqualmie Pass)
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Guye Peak (Snoqualmie pass)
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Lake Chelan, Big Hill
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Lake Creek (Heather Lake trail near Lake Wenatchee)
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Last Chance Mine
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Lost Creek (Bartow pass)
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Magma Mine
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Midnight Mountain
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Moore Prospect
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Orient Gneiss (Orient, WA)
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Railway Dike (Chewelah)
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Riverside (Omak)
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Roosevelt Mine (Republic)
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Sacheen Lake (Spokane)
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Sloan Creek (off Mtn loop Hwy)
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Texas Creek (Winthrop)
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Vesper Peak
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WHAT IS IT USED FOR?
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Jewelry
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Abrasives — sand blasting. Water jet cutting, sandpaper
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Lasers
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Magneto-optical memory
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Water filtration
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Glass polishing & lapping