Precious stones are those which, because of their beauty, hardness, and rarity, are prized for use in ornamentation, especially in jewelry. The diamond, ruby, sapphire, and emerald are the only stones which are, strictly speaking, entitled to be called "precious" in this sense; but the opal, on account of its beauty, is often classed with the precious stones, as is also the pearl, which is really not a stone, but a secretion of a shellfish.

Agate
Alexandrite
Almandine
Amethyst
Aquamarine
Aventurine
Beryl
Bloodstone or Heliotrope
Cameo
Carbuncle
Carnelian
Cat's-eye
Chalcedony
Chrysolite
Chrysoprase
Dendrite
Diamond
Diopside
Emerald
Epidote
Essonite
Flint
Fluorite
Garnet
Hematite
Hyacinth
Idocrase
Indicolite
Iolite
Jade
Jasper
Kyanite
Labradorite
Lapis-lazuli or Lazuli
Moonstone
Nephrite
Obsidian
Olivine
Onyx
Opal
Pearl
Pyrope
Rhondonite
Rock Crystal or Mountain Crystal
Rose Quartz
Rubellite
Ruby
Rutile
Sapphire
Sard
Sardonyx
Spinel
Sunstone
Topaz
Tourmaline
Turquoise
Uralian Emerald
Verd antique
Zircon

From The Standard Dictionary of Facts, The Frontier Press Company, Buffalo, N.Y., 1923.

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“For the word of God is living and active. Sharper than any double-edged sword, it penetrates even to dividing soul and spirit, joints and marrow; it judges the thoughts and attitudes of the heart.”
– Hebrews 4:12