Red, orange and pink parallel lines show through in the twinning in this unheated natural Mozambique ruby. While a relatively common feature in rubies from Mozambique, they generally have to be placed under the dark-field type lighting of a gemological microscope to be seen so easily.

In the rough-gemstone stage, should the twinning be quite prominent, the preforming manufacturer will have to make a hard choice whether to orientate the ruby for either color, or, to minimize the visual impact of the twinning. Given the value of rubies, sometimes these choices need both experience and skill to realize the potential of maximum value.

The formation of such twinning, called ‘polysynthetic twinning’ in this case, whereby an already formed ruby crystal has experienced strain within the crystal which has resulted in some ‘slippage’ manifesting itself as visible lines as shown throughout the ruby.

Technically speaking twinning is not an inclusion in the sense of being a foreign mineral inclusion, but rather is a feature of the ruby itself and cannot be used as clues in diagnostical prognosis for heated or unheated status in natural rubies.

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