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.

    •  
  • 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