Significance of Indranila
Indranila is defined in two contexts according to Purana and Rasashastra. In Purana, it is an epithet for a deep red or dark blue topaz. Meanwhile, Rasashastra describes Indranila as a heavy type of sapphire that exhibits a black lustre from within. Additionally, it is referenced as a color in connection with the sides of Rudhira (carnelian), showcasing a unique hue. Overall, Indranila encompasses both mineral characteristics and color associations in traditional texts.1
The below excerpts are indicatory and do represent direct quotations or translations. It is your responsibility to fact check each reference.
Hindu concept of 'Indranila'
Indranila in Hinduism may represent a distinctive color associated with Rudhira, signify a deep red or dark blue topaz, and denote a heavy sapphire that radiates a black lustre, highlighting its significance in gemstones.
Significance in Rasashastra (chemistry and alchemy):
Rasashastra
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From: Rasa Jala Nidhi, vol 3: Metals, Gems and other substances
(1) A color reference mentioned in relation to the sides of the Rudhira (carnelian), which reflects a distinct hue.[1] (2) A type of sapphire that is comparatively heavy and emits a black lustre from inside.[2]
Significance in Purana and Itihasa (epic history):
Purana
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From: Garuda Purana
(1) An epithet for a type of topaz that is deep red or dark blue.[3]