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Minerals and Metals in Ancient India v2.c43.s3.t2: Corundum, Ruby and Sapphire (9)

Minerals and Metals in Ancient India v2.c43.s3.t2

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Corundum, Ruby and Sapphire (9)

v2.c43.s3.t2.1

It has been indicated in Table 7.2 that pure corundum (*kuruvinda*) is colourless, and specific lattice substitutions in Al₂O₃ induce specific colour and produce gems such as red ruby or *padmarāga*, blue sapphire or *indranīla*, etc. These three minerals have high hardness (9), and only diamond is harder than them (*AM*, 238). Kauṭilya mentioned the use of *kuruvinda* as an abrasive (AS, 2.14.48).

v2.c43.s3.t2.2

Buddhabhaṭṭa made an interesting statement that ruby and sapphire cannot be scratched by any mineral other than diamond and corundum (*RP*, 137); similar statements have been repeated in *GP*, 1.70.27 and *MM*, 213:

v2.c43.s3.t2.3

कुरुविन्दं तथा वज्रं विमुच्य अन्येन केनचित्।
न शक्यं लेखनं कर्तुं पद्मराग इन्द्रनीलयोः।।
*kuruvindaṃ tathā vajraṃ vimucya anyena kenacit*
*na śakyaṃ lekhanam karttuṃ padmarāga indranilayoḥ*

v2.c43.s3.t2.4

Sarma (1984: 51-52) has expressed surprise in the above statements since ruby and sapphire have the same Al₂O₃ lattice as corundum, and are supposed to have similar hardness. However trace substitution by low energy oxides of Cr, Fe etc. might lower surface free energy and hardness of Al₂O₃ by a small amount, and this may be detectable when pure corundum powder is mounted on a grinding wheel. Bauer (1968: 282) has reported slight differences in hardness values of the varieties of corundum, and the fact that ruby is slightly softer than sapphire.

v2.c43.s3.t2.5

*Padmarāga* or red ruby used to come to the ancient India from the gem-beds of Sri Lanka. The valley of the river *Rāvaṇagaṅgā*, overgrown with Areca-palms was strewn with varieties of ruby (*GP*, 1.70.3-17). *Padmarāga* was also known as *māṇikya* and *cunni* (from *cūrṇikā*, small pieces). Best ruby has been described as red like lotus (*padmarāga*), transparent, brilliant, heavy and clear. *Agastimata*, 213 classified ruby on the basis of the amount of radiance emitted above, below and on sides, when held against the sun. If the radiance spreaded all around, indicating lack of crystallinity, then the piece was considered to be spurious (*RYP*, 68).

v2.c43.s3.t2.6

Ruby was known to exist in different shades of red. *Padmarāga* was the red variety with a tinge of white, *nilagandhi* red with a blue or black tint, *saugandhika* yellowish red. The last one was probably known in the West as the orange *padparadsca* (a corrupt form of the word *padmarāga*), the yellowish aurora-red gem from Sri Lanka. (Herbert Smith, Gemstones pp. 289-90) Dull-hued red variety ‘with its lustre remaining within’ was sometimes called *kuruvinda* (*GP*, 1.70.13). Crimson-yellow variety was known as *karundaka* or *kaurandaka* (*MM*, 407; *GP*, 1.74.2). A transparent variety slightly red and yellow was known as *kāṣāyaka* (*RP*, 218; *GP*, 1.74.3). A red variety which appeared to be smeared with milk (*dugdhaliptasma*) was defined as *laśunapadam*, like *laśuna* or garlic (*NRP*, 115).

v2.c43.s3.t2.7

Rose-red balas-ruby belongs to an altogether different category. It is not Al₂O₃ but a spinel or mixed oxide, MgAl₂O₄. It is softer than ruby, its hardness being eight in the Moh’s Scale. Like Al₂O₃, it is colourless when pure, chromium substitution making it red. Spinels come in a wide variety of colours, but here we are concerned with rose-red spinels which have been known as balas-rubies or *rubis balais*. Spinels are abundant in the ruby mines of Badakshan. In the thirteenth century AD, Marco Polo collected spinels with rubies in the province of Balascia on the Upper Oxus, which is identical with the Badakshan of the present-day. Bauer writes (1968: 298) that the term ‘balas-ruby’ is derived from the place-name Balascia. However, we propose that both these names were derived from the Sanskrit term *bālasūryaka*, the crimson-coloured morning sun. Kautilya mentioned *bālasūryaka* as a variety of *padmarāga* or ruby (*AS*, 2.11.29). Thus it is quite likely that ever since Kautilya’s time, the Indians were familiar with the spinel ruby mines of Badakshan. These mines remained famous for more than a millennium. In 1315, Thakkar Pheru wrote:

v2.c43.s3.t2.8

अतितेजः अग्निवर्ण लालं बंदखसाण देशे
*atitejaḥ agnivarnam lālam bandamkhasāṇa deśe*
(*RYP*, 104)

v2.c43.s3.t2.9

At that time, spinel ruby was known as *lāl*. At times, ruby (9), spinel ruby (8), hyacinth variety of zircon (7-1/2) and hessonite variety of garnet (7-1/4), appeared to have similar reddish yellow colour, but these could be easily distinguished from one another by scratch tests since their hardness values (given in parenthesis) are different.

v2.c43.s3.t2.10

*Indranīla* or sapphire was known to the Indians as a different category of gem-mineral (*AS*, 2.11.31), but we know now, that this is blue corundum (vide Table 7.2). According to Buddhabhatta (*RP*, 195-196; also supported in *GP*, 1.72.17-18 and *MM*, 405), a sapphire in which the colours of the rainbow sparkle is an *indranīla*, and the one which turns the milk in a bowl blue, is a *mahānīla*. The Agastimata however labels the second variety as *indranīla* (*AM*, 268), the sapphires from Sri Lanka *mahānīla* and the rest of the sapphires from other sources as plain *nīlas*. Utpala, mentioned in *Arthaśāstra* and *Maṇimālā*, is greenish blue and could be aquamarine rather than sapphire.

v2.c43.s3.t2.11

The *Ratnaśāstra* texts described *indranīla* occurring in different shades of blue, and we know today that sapphire can be deep-blue, the most admired tone being ‘intense cornflower-blue’. Sapphire could be whitish blue leuco-sapphire or *somānaka* (*RP*, 219; *GP*, 1.74.3) or possess a yellowish tinge (‘Oriental topaz’). We have already mentioned that sapphire is slightly harder than ruby (Bauer, 1968: 282). The word ‘sapphire’ came from the old Arabic (also Hebrew) ‘sapeer’ meaning ‘to scratch’, something which is hard. Its hardness enabled it to be distinguished from less hard blue gems like aquamarine, lapis lazuli, and blue-coloured materials like quartz, glass or marble (*GP*, 1.72.14). Garuda Purāṇa mentioned various defects (grain boundary, holes etc.) of some sapphire samples, their occasional contamination with mica and moderate thermal resistance (*GP*, 1.72.6 and 11). The Indians received the best variety of sapphire from the Padmākara province of Sri Lanka (*MM*, 397), which must have been around the modern Ratnapura on the Kaluganga.

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Like blue to yellow transition, sapphire was known to have blue to red transition also, and such reddish blue coloured corundum samples could be called either sapphire or ruby. As a matter of fact, the Arabs guessed (without any scientific knowledge) that sapphires and rubies belonged to a transitional single group of gem mineral, and they called this *Yāqūt* which, according to Al-Afkānī, occurred in seven varieties. (Sarma, 1984:61; Wiedemann, 836-40) Both ruby and sapphire crystals, specially the dark coloured ones, are dichroic, i.e., appearing differently coloured when viewed through mutually perpendicular axes. The famous ‘Sapphire Marveilleux’ appears blue by day and red amethystine by night (*Maṇimālā*, p. 459). Sapphire with a dash of red has been known as *tittibha* (*MM*, 423) A deep blue gem dashed with red was known as *nīlāṅga* or violet-ruby (*Maṇimālā*, part 2, pp. 514-15).

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Asterias or star Sapphire is a special variety which when viewed against light appears like a six-rayed chatoyant star. This is due to the reflection of light from the surface of a multitude or microscopically small tubular cavities or rifts enclosed in the crystal, and grouped into three sets, each of which is parallel to a face of the hexagonal prism. (Bauer, 1968: 284) This variety of *indranīla* was mentioned by Kauṭilya as *śravanmadhya* (AS, 2.11.31) which has been interpreted by one Sanskrit commentator as streaming interior or ‘having rays shooting like flowing water’.

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Most *Ratnaśāstra* texts have discussed the pricing pattern of rubies and sapphires. Sapphire was considered to have different shades of colour which were equated to ‘castes’, e.g., whitish blue (brāhmaṇa), reddish blue (kṣatriya), yellowish-blue (vaiśya) and black-blue (śūdra) etc. (RYP, 82).

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