Considered one of the big three colored stones — along with rubies and sapphires — emeralds are first harvested raw and then cut, shaped and polished for jewelry. Raw emeralds have the same physical qualities as cut emeralds, most obviously a rich green color.
Color, Shape and Clarity
Raw emeralds, like cut emeralds, are all green, but the shade of green varies from blue-green to pale yellow-green to a rich forest green. Like cut emeralds, raw emeralds can be transparent or translucent, a quality that is sometimes called clarity but in the gem trade is referred to as diaphaneity. Raw emeralds have four square corners and grow in columns that range in height. Because the are unpolished, raw emeralds have some roughness and irregularity in patterns along their sides.
Identifying Raw Emeralds
Emeralds are most commonly mined in Brazil, Colombia, Zambia and Zimbabwe, with minor amounts found in a handful of other countries, reports Geology.com. Emeralds that originate from other locations are more likely to be fake. Because they are mined, genuine raw emeralds naturally exhibit irregularities — fake emeralds are molded, so they have few if any irregularities. Real raw emeralds also radiate light when placed in a glass of water, while fake ones do not. A drop of water placed onto the surface of a raw emerald retains its shape, but on a fake emerald it spreads.
References and ResourcesGeology.com: What Are Emeralds?
Sanchez International: Rough Emeralds -- Identifying Real Ones From Fakes
Emerald.org: Emerald Identification