Agate

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Refractive Index : 1.54 – 1.53

Optical Characteristic : AGG

Specific Gravity : 2.60 (+0.30 – 0.05)

Formula : SiO2

Crystal System : Trigonal

Variety/Species : Chalcedony

Species/Group : Cryptocrystalline Quartz

Birefringence : .004

Dispersion : None

Hardness : 6.5 to 7

Toughness : Good

Ultrasonic : Usually Safe

Steam : Usually Safe

UV Long : Inert to moderate

UV Short : Inert to moderate

Pleochroism : None

Strength : N/A

Pleochroism Colors : None

Heat : May change color

Acids : Acids may attack dyes

Light : Stable

Polish Luster : Greasy to vitreous

Fracture : Conchoidal, may be granular

Fracture Luster : Dull to waxy

Clarity Type : N/A

Tones : N/A

Saturations : N/A

Cause of Color : Iron

Enhancements : Dyeing, heating

Cleavage : None or indistinct.

Color Range : Near, colorless, white, brown, yellowish green, green, bluish green, purple, reddish purple, purple-red, red-purple, purplish red, red, orangy red, red-orange, orange-red, reddish orange, orange, yellowish orange, orangy yellow, yellow,greenish yellow, yellow-green, green-yellow, yellowish, purplish, reddish, greenish, orangy, whitish

Transparency : Semitransparent to Opaque

Phenomena : Iris effect

Separations : Agate from-
Obsidian: RI, SG, fracture, optic character (possibly).

Quartz: appearance, RI, birefringence, optic character, SG (possibly), fracture luster.

Moonstone (Orthoclase): phenomenon, polariscope, cleavage, fracture, birefringence (possibly).

Onyx marble: RI, birefrigence, fracture, SG, appearance.

Glass: magnification, fracture luster, (RI, SG, fracture, all, possibly).

Identifying Characteristics and information
Dyed green and dyed blue appear red or pinkish through a chelsea filter. Has curved, angular, or irregular banding in various colors.

Chalcedony is a microcrystalline or cryptocrystalline quartz.

White phosphorescence (rarely).

Spectral Data
Not diagnostic.

Trade Names and Misnomers
Agate
Banded Agate
Lace Agate
Lake Superior Agate

Tags: agate, banded agate, lace agate, lake superior agate