Gemstone Form

Name:

Cordierite (Iolite)

Chem:

Mg2Al3(AlSi9O18)

Crystal:

Orthorhombic (often short prisms)

Color:

Strongly dichroic or trichroic blue - yellow - gray

Refrac. Index:

1.53 - 1.55

Birefraction:

0.008 - 0.012

Hardness:

7 - 7.5

Spec. Grav.:

2.58 - 2.66

Fracture:

conchoidal

Cleavage:

imperfect

Environment:

found in aluminum rich metamorphic rocks

Association:

quartz, andalusite, sillmanite, biotite, spinel, corundum

Locals:

| Conn., N.Y., N.H., Calif., USA | Brazil | Sri Lanka | Burma |

Misc:

One of the names comes from the Greek "ion", meaning "violet", while the name cordierite comes from the French geologist, Pierre Louis Cordier. Another common name is "dichroite" from its strong dichroic nature. Insoluble in acids.

Gem info:

The gem trade has yet another name for this mineral "water sapphire". It is usually cut so that the strongest blue color comes up through the top of the stone. It often shows gray overtones which can detract from its appearance. It is used sparsely in jewelry, and is more of a collectors stone.

blue stone


Name:	Cordierite (Iolite)
Chem:	Mg2Al3(AlSi9O18)
Crystal:	Orthorhombic (often short prisms)
Color:	Strongly dichroic or trichroic blue - yellow - gray
Refrac. Index:	1.53 - 1.55	Birefraction:	0.008 - 0.012
Hardness:	7 - 7.5	Spec. Grav.:	2.58 - 2.66
Fracture:	conchoidal	Cleavage:	imperfect
Environment:	found in aluminum rich metamorphic rocks
Association:	quartz, andalusite, sillmanite, biotite, spinel, corundum
Locals:	\| Conn., N.Y., N.H., Calif., USA \| Brazil \| Sri Lanka \| Burma \|
Misc:	One of the names comes from the Greek "ion", meaning "violet", while the name cordierite comes from the French geologist, Pierre Louis Cordier. Another common name is "dichroite" from its strong dichroic nature. Insoluble in acids.
Gem info:	The gem trade has yet another name for this mineral "water sapphire". It is usually cut so that the strongest blue color comes up through the top of the stone. It often shows gray overtones which can detract from its appearance. It is used sparsely in jewelry, and is more of a collectors stone.
	blue stone