Tourmaline

Name:

Tourmaline

Chem:

(Li,Na,Ca)(Fe,Mg,Mn,Al)3(Al,Fe)6(BO3)3Si6O18(OH,F)4
AluminumBoroSilicate (wide variety of substitutions)

Crystal:

Hexagonal (long prismatic, striated, with a rounded triangular cross section)

Color:

black(schorl), brown(dravite), blue(indicolite), pink(rubellite),green, yellow, orange, multicolor, clear (rare)

Refrac. Index:

1.616 - 1.652

Birefraction:

0.040

Hardness:

7 - 7.5

Spec. Grav.:

3.0 - 3.3

Fracture:

uneven

Cleavage:

none

Environment:

Found in igneous and metamorphic rocks, in shists, pegmatites, and hydrothermal replacement deposits

Association:

lepidolite, microcline, spodumene, andalusite, biotite, quartz, cassiterite, molybdenite

Locals:

| Brazil | Calif., Maine, USA | Sri Lanka | Italy | USSR |

Misc:

The name apparently comes from the Sinhalese word "Turamali" which was given to mixtures of unidentified gem gravels in Ceylon (now Sri Lanka). Insoluble in acids. Strong pyroelectric, and piezoelectric properties. This pressure/electric relationship is used in some high pressure gauges.

Gem info:

Tourmalines come in just about every color in the rainbow. Some of the colors have unique jewelry related names.

Pink to Red tourmaline is known as rubellite, and the color is probably from manganese. It is one of the most valuable of the tourmalines when the colors are dark and rich. Large flawless stones are rare, as the pink variety tends to have more flaws.

Greens - there are two distinct families of green tourmaline, one contains trace amounts of chromium (and coincidentally is called Chrome Tourmaline). It has a high value. Other shades of green may run from light green, to dark olive green and they tend to have less value than the chrome, blue or pinks.

Blue - blue tourmaline is known as indicolite and is highly prized. The best stones are pure blue without hints of green or gray. It tends to be of similar color to dark blue topaz. A new variety of light and very lively blue was discovered in Parabia, Brazil, and has achieved the highest prices paid for tourmaline. Analysis of this material show trace amounts of gold in the structure. Blue stones can be found that are large and flawless. They do not suffer from the poor structure found in rubellite.

Yellow and orange tourmaline maintains intermediate value as long as it does not move into the brown region. Clean yellow and bright orange stones are sought after by collectors and find their way into a small amount of commercial jewelry.

Brown and orange-brown stones are quite common and are not highly valued.

There is a special variety of tourmaline that shows a pink/red interior, and is surrounded by a green exterior "rind". It is called "watermelon" tourmaline, and is often cut and polished flat across a crystal face. It is sometimes cabbed, and even faceted.

Some faceted tourmalines show color changes from top to bottom. Most often these stones are cut into long, rectangular shapes and may display two or more color changes down their long axis. They are usually called bi-colored or tri-colored stones.

Finally, some pinks, yellows, and greens, may show chatoyance, and produce cats-eye cabochons.

green square

yellow triangle

blue rectangle

brown-orange rect.

pink hexagonal

peach oval

mint green pear

bicolor grn/clear rect.
tricolor grn/clear/pink rect
tricolor peach/blue/grn rect
watermelon slices
watermelon cab


Name:		Tourmaline
Chem:		(Li,Na,Ca)(Fe,Mg,Mn,Al)3(Al,Fe)6(BO3)3Si6O18(OH,F)4 AluminumBoroSilicate (wide variety of substitutions)
Crystal:		Hexagonal (long prismatic, striated, with a rounded triangular cross section)
Color:		black(schorl), brown(dravite), blue(indicolite), pink(rubellite),green, yellow, orange, multicolor, clear (rare)
Refrac. Index:		1.616 - 1.652	Birefraction:	0.040
Hardness:		7 - 7.5	Spec. Grav.:	3.0 - 3.3
Fracture:		uneven	Cleavage:	none
Environment:		Found in igneous and metamorphic rocks, in shists, pegmatites, and hydrothermal replacement deposits
Association:		lepidolite, microcline, spodumene, andalusite, biotite, quartz, cassiterite, molybdenite
Locals:		\| Brazil \| Calif., Maine, USA \| Sri Lanka \| Italy \| USSR \|
Misc:		The name apparently comes from the Sinhalese word "Turamali" which was given to mixtures of unidentified gem gravels in Ceylon (now Sri Lanka). Insoluble in acids. Strong pyroelectric, and piezoelectric properties. This pressure/electric relationship is used in some high pressure gauges.
Gem info:		Tourmalines come in just about every color in the rainbow. Some of the colors have unique jewelry related names. Pink to Red tourmaline is known as rubellite, and the color is probably from manganese. It is one of the most valuable of the tourmalines when the colors are dark and rich. Large flawless stones are rare, as the pink variety tends to have more flaws. Greens - there are two distinct families of green tourmaline, one contains trace amounts of chromium (and coincidentally is called Chrome Tourmaline). It has a high value. Other shades of green may run from light green, to dark olive green and they tend to have less value than the chrome, blue or pinks. Blue - blue tourmaline is known as indicolite and is highly prized. The best stones are pure blue without hints of green or gray. It tends to be of similar color to dark blue topaz. A new variety of light and very lively blue was discovered in Parabia, Brazil, and has achieved the highest prices paid for tourmaline. Analysis of this material show trace amounts of gold in the structure. Blue stones can be found that are large and flawless. They do not suffer from the poor structure found in rubellite. Yellow and orange tourmaline maintains intermediate value as long as it does not move into the brown region. Clean yellow and bright orange stones are sought after by collectors and find their way into a small amount of commercial jewelry. Brown and orange-brown stones are quite common and are not highly valued. There is a special variety of tourmaline that shows a pink/red interior, and is surrounded by a green exterior "rind". It is called "watermelon" tourmaline, and is often cut and polished flat across a crystal face. It is sometimes cabbed, and even faceted. Some faceted tourmalines show color changes from top to bottom. Most often these stones are cut into long, rectangular shapes and may display two or more color changes down their long axis. They are usually called bi-colored or tri-colored stones. Finally, some pinks, yellows, and greens, may show chatoyance, and produce cats-eye cabochons.
		green square	yellow triangle	blue rectangle	brown-orange rect.
	pink hexagonal	peach oval	mint green pear	bicolor grn/clear rect. tricolor grn/clear/pink rect tricolor peach/blue/grn rect watermelon slices watermelon cab