Volume 20 Nos. 7 & 8 July & October 1987

'•'^Journal of Gcmmology

Contents

Editorial 402

Blue spinel from the Hunza valley, Pakistan

R.R. Harding and F. Wall 403

Notes from the Laboratory - 1 1 K. Scarralt 406

The sale of the Windsor jewels A.Gray 423

Blue and yellow sapphire from Kaduna Province,

Nigeria L. Kiefert and K. Schmelzer ATI

In the witness box E. Bruton 443

The emeralds of the Belmont Mine, Minas Gérais, Brazil H.A. Hänni, D. Schwarz and M. Fischer 446

The separation of natural from synthetic diamonds using the Barkhausen effect

The body colour of gemstones

Further development of a computer program for gem identification

Internal diffusion

The background to diamond grading

Some DIY gemmological instruments

A cheap dichroscope

An account of chrysoberyl-bearing pegmatite near Pattara, Sri Lanka

Gemmological Abstracts

Book reviews

Proceedings of the Gemmological Association of Great Britain and Association Notices 503

Copyright (€) 1987

Gemmological Association of Great Britain

Registered Office: Saint Dunstan's House, Carey Lane, London EC2V 8AB

ISSN: 0022-1252

D. Minster

J.B. Nelson

P.O. Read

J.I. Koivula

B.C. Emms

J. Eadic

N. Grist

E.G. Zoysa

458

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467

474

478.

482

485

486

490

499

Produced by Green Belt Studios: Printed by Quadrant Offset, Hertford, England.