How to Buy Opals

Some basic factors to consider when buying Opal

  • Fire type: harlequin (which type?), flash, broadflash, large or small pin, combinations, or?
  • Colors: red (which type, magenta, etc.), green, blue, purple, gold, etc. predominance, combinations.
  • Base color: black, grey, degree of blackness, crystal, jelly, white,off-white, yellow, brown, etc.
  • Thickness of the color bar, consistency all around the piece,
    interplay of the various color bars, top or side cutting.
  • Brilliance.
  • Equipment, etc: High speed, low speed, diamond vs Carborundum. How you handled the opal when grinding. Heat and amount of water used in cutting.
  • Your skill: hobbyist, beginner, intermediate, expert, designer,
    dealer.
  • What you want to do with the opal: standard cabs, free form,
    inlay, composites, doublets, triplets.
  • Source: fields, depth of mining, methods of mining: Buy nothing
    from New Field at Coober Pedy area or Mehi at Lightning Ridge. It helps to know your supplier.
  • Storage and transport methods: (Safe deposit boxes are not safe
    for opal when left dry. Call for an explanation.)
What follows is the primary factors in determining the value of rough opal… but there’s a lot more to this than meets the eye! We’ve also included a text file that you can download and take with you to the next gem show you attend. This will explain a lot of terminology and help you understand why certain properties are valuable and others are not.

Click here to download the Opal Buying Guide

FACTOR DESCRIPTION VALUE
Base
Color and Degree of Translucence
White
or Jelly (opaque)
GreySemi-black

Near Clear

Crystal Black

Black (jet)

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Fire
Color
size=”4″>GreenBlueBlue-Green

Red-Green

Multicolor (3, 4, or 5 colors)

Red predominant, multicolor

Magenta and True Purple (very rare)

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Fire
Pattern
SunflashPinfireBroad flashes

Rolling flashes

Harlequin

(hard angled fire pattern visible from all angles)
Broad rolling flashes

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Fire
Intensity
Very directional with
dead areas
Low intensityNo directionality

(shows fire from all angles)
High intensity

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FACTOR LEAST
VALUABLE
MOST
VALUABLE
Quality
of fire
band in rough
Thin <FONT
size=”2″>(triplets,
dome cabs)

Thick(high domed or flat stones) 

Penetration Partial
penetration
of fire band

Penetration to whole
outside periphery
Waste Little
fire in relation to
waste – spare fire, large waste

More fire, less to
little waste
Straightness Fire band
not straight or poor shape of rough relative to band

Fire band or bands
straight
Intensity Fire intensity
muted or not bright

Brilliant intensity

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