Comparison of Diamond and Simulated Diamond Gemstones

Home , Conchoidal fracture, Heliotrope (mineral)

CAMEO: Conservation and Art Materials Encyclopedia Online at cameo.mfa.org

Properties of Gemstones page 1

Mineral Gem Color Mohs Specific Refractive index Crystal system Other Fluorescence Dispersion Inclusions hardness gravity

beryl aquamarine sky blue 7.5-8.0 2.68-2.71 epsilon = hexagonal crystal transparent; none to weak; Aquamarines 1.570-1.580 system; conchoidal weakly synthetic are often goshenite colorless omega = fracture pleochroic stones may flawless; heliodor yellow 1.574-1.586 appear opaque Other contain and dull red in many emerald green 2.68-2.78 epsilon = longwave UV inclusions such 1.571-1.581 as mica, pyrite omega = and calcite 1.577-1.588 morganite pink 2.66-2.83 epsilon = 1.580-1.590 omega = 1.589-1.601 chrysoberyl alexandrite green in daylight, red in 8.5 3.5-3.8 alpha = 1.745 orthorhombic, transparent; strongly d = 0.015 incandescent light beta = 1.748 flattened crystals, chrysoberyl pleochroic gamma = 1.754 often twinned cat's-eye is chatoyant cristobalite opal milky white to colorless;; 5.5-6.5 1.98-2.25 1.435-1.455 tetragonal opaque; may fluoresce possible variable pale shades submicrocrystalline contains some white or pale aggregates; water causing green; may irregular the physical phosphoresce concretions; glass- properties to like fracture vary corundum sapphire blue 9.0 4.0 epsilon = hexagonal; transparent; orange to red; d = 0.018 many 1.757-1.768 conchoidal fracture marked heat treated including ruby red omega = dichroism stones may minerals padmaradschah orange 1.765-1.776 fluoresce green (rutile), fluids, angular banding diamond diamond variable (colorless, 10.0 3.52 2.4175 isometric flattened transparent; may fluoresce d = 0.044 trigonal on yellow, blue) octahedrons; perfect cleavage pale colors in surface; dodecahedrons in four longwave UV; numerous directions may inclusions phosphoresce potash orthoclase pale yellow to flesh red 6.0-6.5 2.6 alpha = 1.518 monoclinic crystals two perfect feldspar beta = 1.522 cleavages at gamma = 1.522 right angles

moonstone colorless, white to nodules or masses blue yellowish opalecsence amazonite yellow green to blue triclinic, large variety of green crystals microcline

plagioclase sunstone colorless to pale pink 6.0-6.5 2.6-2.7 alpha = triclinic prismatic transparent to inclusions give feldspar (aventurine) 1.527-1.577 crystals; two perfect opaque; spangled beta=1.531-1.585 cleavages at right iridescent; appearance gamma = angles labradorite grayish shades 1.538-1.590 fluorite fluorite lavender to green 1.434 conchoidal fracture transparent strong color zoning

Properties of Gemstones page 2 Mineral Gem Color Mohs Specific Refractive index Crystal system Other Fluorescence Dispersion Inclusions hardness gravity

garnet almandine deep red with a trace of 7.0-7.5 4.3 1.79-1.83 isometric euhedral light colored none d = 0.024 needles; (carbuncle) purple crystals, with varieties are single and dodecahedrons and transparent; no multiphase andradite (Uralian deep emerald-green 6.5-7.0 3.9 1.887 none d = 0.057 trapezodrons most birefringence, prisms emerald) common; no pleochroism grossularite yellow-brown to orange, 7.0-7.5 3.6 1.734-1.740 conchoidal fracture pale orange in d = 0.028 (hessonite) red, or green long UV; yellow in short UV

pyrope dark blood red 7.0-7.5 3.78 1.714-1.742 none d = 0.027 spessartine yellow-orange to brown- 7.0-7.5 4.15 1.800-1.810 none d = 0.027 red jade jadeite (Imperial green but may be white, 6.0 3.33-3.34 alpha = monoclinic compact translucent to may have pale jade) black, red, brown, yellow, 1.640-1.658 or fibrous masses; opaque; greasy white color in blue or mauve beta=1.645-1.663 granular to splintery luster long UV light gamma = fracture 1.652-1.673 nephrite deep spinach green to 6.0-6.5 2.96-3.02 alpha = monoclinic compact translucent to none some dark near-white 1.600-1.672 masses; conchoidal opaque; greasy inclusions beta=1.614-1.686 to granular fracture or waxy gamma = appearance 1.627-1.693 lazurite lapis lazuli azure blue with flecks of 5.0-5.5 2.7-2.9 1.50-1.67 isometric with decomposed by white and gold compact masses; hydrochloric opaque acid olivine peridot; chrysolite yellow green; dark bottle 6.5-7.0 3.3-3.4 alpha = orthorhombic transparent d = 0.020 green; olive green 1.635-1.671 system with beta = massive or granular 1.652-1.698 forms; gamma = fracture=uneven to 1.671-1.707 conchoidal quartz amethyst purple 7.0 2.65 epsilon = 1.553 conchoidal fracture transparent; d = 0.013 omega = 1.544 heat treatment cairngorm (smoky smoky brown may bleach quartz) stones citrine yellow rock crystal colorless rose quartz pink agate (moss agate, variable compact masses; translucent to mocha stone) nodules opaque

chalcedony (onyx, variable carnelian, sardonyx, chrysoprase, bloodstone, heliotrope) jasper variable

Properties of Gemstones page 3 Mineral Gem Color Mohs Specific Refractive index Crystal system Other Fluorescence Dispersion Inclusions hardness gravity

spinel Balas ruby; typically red; also 8 3.6 1.715-1.725 isometric octahedral transparent natural d = 0.020 fingerprint variable: yellow crystals; rounded fluoresces red pattern (rubicelle), violet grains; conchoidal in longwave inclusions (almandine), pleonast fracture UV; synthetic (blue, black), gahnite may show (blue-green) colors in shortwave UV topaz topaz, hyacinth yellow, green, blue, violet 8 3.4-3.6 alpha = orthorhombic transparent; may fluoresce d = 0.014 single and or red 1.606-1.629 prismatic crystals; highly yellow in multiphase beta = .609-1.631 perfect cleavage in pleochroic; longwave UV gamma = one direction turns soft red 1.616-1.638 when heated tourmaline achroite colorless or green 7-7.5 2.9-3.2 epsilon = hexagonal prismatic transparent; none to weak d = 0.016 gas and liquid 1.610-1.650 crystals, often pleochroic pockets with dravite brown omega = rounded or oval; color zoning indicolite blue 1.635-1.675 conchoidal fracture rubellite pink schorl black siberite violet turquoise turquoise blue to greenish-blue 5.0-6.0 2.6-2.9 alpha = 1.61 cryptocrystalline to opaque; color beta = 1.62 fine granular; fades in sunlight gamma = 1.65 fracture=conchoidal

zircon jargon variable 6.0-7.5 4.6-4.7 epsilon = tetragonal system transparent; some show dull d = 0.048 rutile crystals; 1.968-2.015 with square pleochroic yellow color; single and Matura diamond colorless omega prismatic crystals; some may multiphase hyacinth yellow orange = 1.923-1.960 fracture=uneven phosphoresce jacinth red brown