Presentation on theme: "1 Presented by – Mr.Upali Nandalal Gemmologist. Historical background of Padmaraga The name derives from the Sinhalese word for Lotus blossom, from time."— Presentation transcript:
1 Presented by – Mr.Upali Nandalal Gemmologist
Historical background of Padmaraga The name derives from the Sinhalese word for Lotus blossom, from time to time. It changes as Pathmaraja according to the Sanskrit language. Pathmaraja, Padmaraga and Padmaradscha are words referred to the same stone. 2
Corundum Family a) Ruby b) Blue Sapphire c) Pink Sapphire d) Yellow Sapphire e) Orange Sapphire f) Padmaraga g) Purple Sapphire h) Green Sapphire i) White Sapphire j) Star Sapphire k) Colour Changing Sapphire 3
Properties of Corundum family 1) Chemical composition- Al 2 O 3 (Aluminum Oxide) 2) Crystal System- Trigonal 3) Crystal habit- Barrel shape 4) Hardness- 9.0 (Mohs scale) 5) Specific Gravity - 3.99 6) Refractive Index - 1.762 – 1.770 7) Birefringence- 0.008 8) Optic sign - Uniaxial – (Negative) 9) Cleavage- None 10) Fracture - Conchoidal, Splintery 11) Luster - Vitreous 12) Streak - White 4
Padmaraja is a Pink – Orange Sapphire, originally being mined in Sri Lanka, but also found in Gem deposits of Madagascar, Tanzania and a few in Vietnam and Africa. Padmaraga (Sapphire) is very Rare and therefore highly valued. 5
Behavior of Light rays within Gemstones Singly Refractive Doubly Refractive A light ray entering into a Doubly Refractive Gemstone will split into two rays with two different velocities and vibrational directions (Other than parallel to the optic axis). 6
As corundum belongs to Doubly Refractive category, light will behave in the same manner. Corundum with a single colour (e.g. :- Blue Sapphire and Ruby) the colour splits into two colours. 7
Atomic structure of Corundum (without colouring elements) 8 1) Colourless Corundum (White Sapphire) Pure Aluminum Oxide without colouring elements.
Possible sites of Colouring elements. Possible sites of Colouring elements. 9
10 Pink Sapphire Substitution positions are occupied by Chromium atoms (randomly) [Lesser number of Chromium atoms, which are not enough to create deep red colour of Ruby.]
11 Yellow Sapphire Substitution positions are occupied by Iron atoms (randomly) [further the yellow colour of Sri Lankan Yellow Sapphires is also produced by colour centers].
12 Substitution positions are occupied by a lesser number of Chromium atoms and Iron atoms (Colour Centers could also produce yellow colour). Orange Sapphire
13 Patchy Orange colouration of Pink Sapphire creates Orangish Pink Sapphire, Which is called Padmaraga Padmaraga
14 Yellow Sapphire Substitution positions are occupied by Iron atoms (randomly) [further the yellow colour of Sri Lankan Yellow Sapphires is also produced due to colour centers. Pink Sapphire Substitution positions are occupied by Chromium atoms (randomly) [Lesser number of Chromium atoms which are not enough to create deep red colour of Ruby.] Substitution positions are occupied by a lesser number of Chromium atoms and Iron atoms + Colour Centers. Orange Sapphire Patchy Orange colouration of Pink Sapphire creates Orangish Pink Sapphire, Which is called Padmaraga
Colour distribution of Blue Sapphire Distribution of Blue colour is shown in this picture. Distribution of Pink and Orange colourations although not commonly visible, it is assumed to be in the same manner. 15 Patchy colouration of Padmaraga.
Variations of Pink and Orange Colour Intensities. 16
1. Pink with a low intensity of Orange colouration. Colour is evenly distributed but intensity of Orange is very very low. Therefore the stone can not be classified as Padmaraga 17
2. Light Purplish pink with a highly intensed patchy Orange Colouration. 2. Light Purplish pink with a highly intensed patchy Orange Colouration. Orange Colour is patchy. As the colour patch is located close to the culet, the colour gets dispersed throughout the stone, showing Orangish Pink through the table. Therefore it could be classified as Padmaraga. 18
3. Purplish Pink with low intensity of Orange colouration 3. Purplish Pink with low intensity of Orange colouration. could not be Here, Orange colouration is masked by high intensity of Purplish Pink colouration of the stone. Therefore it could not be classified as Padmaraga. 19
4. Pinkish Orange – Padmaraga Both Pink and Orange colours are evenly distributed throughout the stone. But intensity of the Orange colour is higher than Pink. It is termed Pinkish Orange Sapphire. If the intensity of Pink colour is higher than orange, it is termed Orangish Pink Sapphire. 20
This is the ideal colour balancing of Padmaraga. When both Pink and Orange Colour components are there in equal proportions (50% - 50%), then the stone is termed Pink/Orange Sapphire or Orange/Pink Sapphire. This is the ideal colour balancing of Padmaraga. 21
Colouration of Padmaraga could also vary in following manner. 1. 30% Orange + 70% Pink 2. 70% Orange + 30% Pink There could be varying proportions of Pink/Orange colourations which could also be considered as Padmaraga. 22 30% - 70% 70% - 30% 50% - 50% Pink Orange (Orangish Pink) (Ideal colour of Padmaraga) (Pinkish Orange)
Pink prominent Padmaraga is preferred by Japanese buyers. Orange prominent Padmaraga is preferred by German and European buyers. 23 Orangish pink Padmaraga 50 – 50 % Padmaraga Pinkish Orange Padmaraga
Colouring elements in Corundum Ruby- Cr 3+ Blue - Fe 2+ / Ti 4+ Yellow- Fe 3+, Colour centers Orange- Cr 3+, Fe 3+, Colour centers Padmaraga- Cr 3+, Fe 3+, Colour centers Green - Fe 2+ Purple- Cr 3+, Fe 2+, Ti 4+ Pink- Cr 3+ 24
Colour Centers 25 Electron imbalance of crystal lattice, creates colour centers. It may be naturally occurring or could be created by supplying energy.
References Hughes. W. Richard, Ruby and Sapphire, USA, 1997, 01 st edition, 51, 57, 83, 109, 200, 398 pp Dharmaratne. P.G.R., Gemmology, Sri Lanka, 2007, 01 st edition, 39 p. Hughes. W. Richard, Walking the line in ruby and Sapphire, www. Palagems.com Hughes. W. Richard, www. Palagems.com Padparadscha Sapphire buying Guide. Webster Robert, Gemmologists Compendium, 1970, 01 st edition, 161 p. Read Peter G, Gemmology, 2006, Third edition, 70 p, Read Peter G, Dictionary of Gemmology, 1982, 01 st edition, 45 p. 27