THE JGRL GEM LIBRARY
Get to know gemstones.
Discover the reasons for their beauty.
The structure behind a color. The place a gem formed. The cut that brings out its light.
A collection of fundamentals to help you understand each stone.
Crystals / Origins / Colors / Hardness / Cuts
EXPLORE THE GEMSTONES
Explore gemstones
Search by name or color to discover a gemstone.
Ruby
Ruby
The red variety of corundum, colored by chromium. Sapphire belongs to the same mineral species.
- Mohs hardness
- 9
- Crystal system
- Trigonal
Sapphire
Sapphire
Corundum in a wide range of colors, not only blue. Red corundum is classified separately as ruby.
- Mohs hardness
- 9
- Crystal system
- Trigonal
Emerald
Emerald
Green beryl colored by chromium or vanadium. Aquamarine and morganite are varieties of the same mineral.
- Mohs hardness
- 7.5–8
- Crystal system
- Hexagonal
Diamond
Diamond
A gemstone composed of carbon, known for high hardness and the reflection and dispersion of light through its polished facets.
- Mohs hardness
- 10
- Crystal system
- Cubic (isometric)
Aquamarine
Aquamarine
Blue beryl with a sea-like color. It shares a mineral species with emerald, while its color and inclusion characteristics differ.
- Mohs hardness
- 7.5–8
- Crystal system
- Hexagonal
Morganite
Morganite
Beryl with a gentle pink color related to manganese. Large stones with attractive transparency are also known.
- Mohs hardness
- 7.5–8
- Crystal system
- Hexagonal
Spinel
Spinel
A distinct mineral whose red stones were sometimes confused with ruby in history. Blue, gray and many other colors are also found.
- Mohs hardness
- 8
- Crystal system
- Cubic (isometric)
Alexandrite
Alexandrite
Chrysoberyl whose apparent color changes with the light source. The strength of the change differs between stones.
- Mohs hardness
- 8.5
- Crystal system
- Orthorhombic
Chrysoberyl Cat’s-eye
Chrysoberyl Cat’s-eye
Chrysoberyl displaying a single luminous band. The term cat's-eye also describes an optical effect seen in other materials.
- Mohs hardness
- 8.5
- Crystal system
- Orthorhombic
Garnet
Garnet
A gemstone group extending far beyond red, including green tsavorite and demantoid.
- Mohs hardness
- 6.5–7.5
- Crystal system
- Cubic (isometric)
Peridot
Peridot
A yellow-green gem whose color relates to iron in its mineral composition, with a characteristic fresh olive hue.
- Mohs hardness
- 6.5–7
- Crystal system
- Orthorhombic
Amethyst
Amethyst
Purple quartz, sharing its mineral identity with citrine. Color zoning and growth patterns may be present.
- Mohs hardness
- 7
- Crystal system
- Trigonal
Citrine
Citrine
Yellow to orange quartz. It is a different mineral from topaz, even when their colors look similar.
- Mohs hardness
- 7
- Crystal system
- Trigonal
Topaz
Topaz
A gem available in blue, pink, colorless and other colors, extending well beyond the yellow traditionally associated with its name.
- Mohs hardness
- 8
- Crystal system
- Orthorhombic
Tourmaline
Tourmaline
A mineral group with a rich color range. Some individual crystals display several colors together.
- Mohs hardness
- 7–7.5
- Crystal system
- Trigonal
Tanzanite
Tanzanite
The blue-to-violet variety of zoisite, commercially sourced from the Merelani area in northern Tanzania.
- Mohs hardness
- 6–7
- Crystal system
- Orthorhombic
Opal
Opal
A hydrated silica gem. Moving flashes of color, known as play-of-color, are a celebrated characteristic of some varieties.
- Mohs hardness
- 5–6.5
- Crystal system
- Amorphous
Jadeite Jade
Jadeite Jade
Jade can be white or lavender as well as green. Jadeite jade and nephrite jade are distinct materials.
- Mohs hardness
- 6.5–7
- Crystal system
- Monoclinic
Pearl
Pearl
A gem produced through biological processes. Properties vary with the mollusk and freshwater or saltwater environment.
- Mohs hardness
- 2.5–3
- Crystal system
- Layers of microcrystals and organic material
Zircon
Zircon
A natural mineral capable of strong brilliance. It is a different material from manufactured cubic zirconia (CZ).
- Mohs hardness
- 6–7.5
- Crystal system
- Tetragonal
Illustrations suggest color and shape. Individual stones vary; each gem page includes further details and references.
A LITTLE KNOWLEDGE, A DEEPER APPRECIATION
The more you know,
the more there is to discover.
How do hardness and toughness differ?
Understand the language of gems, one idea at a time.