Garnet

Garnet from Lake Creek near the Heather Lake trail (west of Lake Wenatchee)

WHAT IS IT?

• 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⁺)

• The birthstone for January

• The name comes from the Latin word “Garanatus”, meaning ”seedlike”, or like the seeds of a pomegranate.

HISTORY

• Used Since the Bronze Age

• A garnet bead necklace has been found in a 3000 BC grave

• Plato had his portrait engraved onto a garnet

• In Bohemia (part of the modern Czech Republic), castles and churches are decorated with Garnets

• Bohemian garnets are still used in traditional jewelry

• In medieval times, garnets were believed to cure depression

• Garnet is one Of the 12 gemstone on Aaron’s breastplate

WHAT TYPES ARE THERE?

• Colors: red, pink, orange, yellow, green, blue, brown, black. Red to reddish purple is the most common.

• There are different types that possess similar physical properties & crystalline form but different chemical compositions

• Garnets can be natural or synthetic

• 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)

• Almandine -Fe₃Al₂Si₃O₁₂

  • Gemstones of this type are a transparent deep red and are called “Carbuncle”. They occur in metamorphic rock such as mica schists.

• Andradite - Ca₃Fe₃₊ ₂Si₃O₁₂

  • 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

• Grossular - Ca₃Al₂Si₃O₁₂

  • 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

  • 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.

• Spessartine - Mn₃Al₂Si₃O₁

  • 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.

• Uvarovite - Ca₃Cr₂Si₃O₁₂

  • A rare garnet having bright green coloring

• There are other less common species of garnet:

  • Calcium in X site

  • Hydroxide bearing with calcium in X site

  • Magnesium or manganese in X site

WHERE IS IT FOUND?

• The largest producers: Australia.

• Other producers: China. U.S.

• Collection sites in Washington State -

  • Barclay Creek (Halford.WA)

  • Buckhorn Mountain

  • Deer Trail. Monitor Mine

  • Denny Mountain (Snoqualmie pass) — Grossular garnet

  • Garnet Creek (Barlow Pass)

  • Gaynor (Snoqualmie Pass)

  • Guye Peak (Snoqualmie pass)

  • Lake Chelan, Big Hill

  • Lake Creek (Heather Lake trail near Lake Wenatchee)

  • Last Chance Mine

  • Lost Creek (Bartow pass)

  • Magma Mine

  • Midnight Mountain

  • Moore Prospect

  • Orient Gneiss (Orient, WA)

  • Railway Dike (Chewelah)

  • Riverside (Omak)

  • Roosevelt Mine (Republic)

  • Sacheen Lake (Spokane)

  • Sloan Creek (off Mtn loop Hwy)

  • Texas Creek (Winthrop)

  • Vesper Peak

WHAT IS IT USED FOR?

• Jewelry

• Abrasives — sand blasting. Water jet cutting, sandpaper

• Lasers

• Magneto-optical memory

• Water filtration

• Glass polishing & lapping