_Balas ruby_: Red _Almandine spinel_: Purple red _Rubicelle_: Orange _Sapphire spinel and ghanospinel_: Blue _Chlorspinel_: Green [Illustration: Candelabra: white quartz, blue-capped red elbaite, and tan albite, California.] Topaz (hardness: 8 Mohs) Aluminum silicate fluoride hydroxide Specific gravity: 3.5-3.6 Wine yellow, pale blue, green, violet, or red Tourmaline (hardness: 7-7.5 Mohs) Complex aluminum borosilicate (Elbaite, Dravite, Uvite) Specific gravity: 3.03-3.25 _Achorite_: Colorless _Brazilian emerald_: Green _Dravite_: Brown _Indicolite_: Dark blue _Rubellite_: Pink to red _Siberite_: Violet _Verdilite_: Green Turquoise (hardness: 5-6 Mohs) Hydrous copper aluminum phosphate Specific gravity: 2.6-2.8 Sky blue; greenish blue Zircon (hardness: 7.5 Mohs) Zirconium silicate Specific gravity: 4.6-4.7 _Jargon_: Variable _Matura diamond_: Colorless _Hyacinth_: Yellow, orange, red, brown [Illustration: The Hooker Emerald, Colombia.] Birthstones Month of birth Gemstone Color January Garnet Dark red February Amethyst (Quartz) Purple March Aquamarine (Beryl) or Bloodstone Pale blue (Quartz) April Diamond or Rock Crystal (Quartz) Colorless May Emerald (Beryl) Bright green or Chrysoprase (Quartz) Pale green June Pearl or Moonstone (Feldspar) Cream July Ruby (Corundum) or Carnelian Red (Quartz) August Peridot Pale green or Sardonyx (Quartz) Brown and white September Sapphire (Corundum) Pale to dark blue or Lapis Lazuli Deep blue October Opal or Tourmaline Variegated November Topaz or Citrine (Quartz) Yellow December Turquoise Sky blue Organic gemstones The four organic gemstone groups listed below are highly prized for their beauty and rarity. However, they are not as durable as gemstones from minerals: Amber (hardness: 2-2.5 Mohs) A mixture of hydrocarbons Specific gravity: 1.05-1.096 Hard fossil resin or sap of ancient pine trees. Usually amorphous (lacks crystalline structure). Sometimes mined, sometimes gathered on seashores. Varies from transparent to semitransparent and generally from light yellow to dark brown, but can be orange, red, whitish, greenish-brown, blue, or violet. Can be dyed in any color. Takes a fine polish. Used mainly in making beads or other ornaments.