Topaz , meaning of topaz, its chemistry, crystal system, varieties , physical & optical properties, treatment and identification

TOPAZ

The meaning of Topaz is to seek, to search or fire.

(The state gemstone for the US state of Utah.)

Chemistry:

Aluminum fluo-silicate - A12 (F, OH) 2SiO4

 Crystal system and habit:

Orthorhombic: Usually found as elongated prisms with a

 rhomb - shaped cross section. The prisms will frequently show

 vertical striations. Also found as rolled pebbles.

orthorhombic Topaz crystal system 

orthorhombic Topaz crystal system 

orthorhombic Topaz crystal system 

Topaz crystals with faceted topaz 

Pink Topaz lot from Katlang, Mardan, KPK, Pakistan 

Pink Topaz lot from Katlang, Mardan, KPK, Pakistan 

Topaz crystal

Pink Topaz from Katlang, Mardan, KPK, Pakistan 

Varieties: Transparent to translucent.

•    Topaz (use with color prefix)-colorless Yellow to orange ('sherry' brown)  and brownOrange topaz, the state gemstone for the US State of Utah •    Pink and red (rare) (color due to chromium). •    Blue and blue-green (resembling aquamarine).
Phenomena:
Topaz Cat's-eye (blue and yellowish-orange stones - rare).
Physical properties:
Cleavage Fracture Hardness	Perfect basal, easy Conchoidal 8
Specific Gravity	Blue, yellow & white (F) 3.56	Orange, red & pink (OH)
		3.53
Refractive Index	1.61 - 1.62	1.63-	1.64
Birefringence	0.010	0.008
Optical Nature Dispersion	Biaxial, positive Low (0.014)
Pleochroism Luster	Distinct in well colored stones Vitreous

Occurrence:

 

Brazil, Nigeria, Australia, Sri Lanka, Pakistan, Burma, USA, Mexico, and Namibia. (Colorless stones for treatment come mostly from Nigeria and Sri Lanka).

Other points:

·     Durability: Fair.

·     Birthstone: November.

 

Inclusions:

 fluids, 2 or multi-phase inclusions: occasional crystals inclusion and rare unusual tripolite mineral inclusion in topaz from Pakistan.

Spectrum : 

Pink Topaz Spectrum (Dark Pink)

 

Enhancement: Topaz is sometimes seen in various shades of pink and, in a large percentage of cases, this color is artificially induced. It is produced by heat treatment of 'sherry' brown ('pinked'') stones (color is stable).

yellowish orange topaz is heated to conver in pink topaz

Buy natural unheated Pink topaz on ebay shop

Buy Natural unheated certified pink topaz

Currently much treated blue topaz is also met with on the market.* , Pale blue or colorless material is irradiated which, with subsequent heat treatment, induces a handsome blue color (stable) or green (unstable). Depending to a certain extent upon the type of treatment used, light to medium 'aquamarine' blue is produced as well as 'super' blues not met with in nature.

Colorless topaz after irradition treatment 

Cut:

Step and mixed cut common. Care must be taken when cutting to make sure that a facet is worked at a slight angle to the cleavage plane (which doesn't take a good polish). Cabochon for slightly included material.

Some common questions about Topaz

How do I know if a topaz is “Imperial topaz”?

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There is no official standard for Imperial topaz. Some dealers use the term for colors that are orange to pink to red to purple; others reserve the term for certain saturated shades. It’s the color, not the term “Imperial,” that gives topaz its value.

Is pink topaz from Pakistan or Brazil more valuable?

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Color is more important than country of origin in assessing topaz quality. The rarest color of topaz is a vivid purplish pink.

Is blue topaz radioactive?

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National regulations around the world control the release of gems from irradiation facilities to ensure that they meet safety standards. In the United States, the standard for release and import of topaz is a small fraction of the background radiation that everyone is exposed to every day.