Symbolism of Gems, etc.
In Christian art, gems, metals and colours are invested with symbolic meaning. The amethyst signifies humility, the Diamond—Invulnerable Faith, the Sardonyx—Power, the Sapphire—Hope, Gold represents Power or Glory, and Silver—Purity.
Black represents Grief or Death, Blue—Hope and Divine Contemplation, pale blue—Peace, Christian Prudence or a serene conscience, Green—Faith, Gladness, pale green—Baptism, Grey—Tribulation, Purple—Justice or Royalty, Red—Martyrdom for Faith, Scarlet—Fervour, and glory of witnesses to the Church, Violet—Penitence, and White—Purity, Temperance and Innocence.
Shells on tombstones are allusive to the earthly body left behind, a mere shell of the immortal soul. They are also used to indicate a pilgrim, by whom they were carried, probably as a drinking vessel or form of spoon.
Torches, either upright or inverted, symbolised respectively Life and Death. When in the latter position the flame is represented as ascending, the significance is Death with hope of the Resurrection. An earlier signification in Pagan art is the bridal torch of Hymen.