NACRE :
French for mother-of-pearl

NACREOUS FELDSPAR :
Synonym of Moonstone.

NADELEISENERZ :
German Name for Goethite.

NAEGITE :
Variety of green Zircon from Japan; this stone is highly radioactive.

NAESUMITE :
Altered Cordierite

NAPOLEONITE :
Old Appellation for Orthose.

NAPOLITE :
Synonym of Haüyn also called Haüynite.

NA-SPODUMENE :
Original Name for Spodumene containing Sodium.

NATIVE PRUSSIAN BLUE :

(English) Synonym for vivianite.

NATROCALCITE :
Synonym of Datolithe.

NATROLITE :
Fibrous mineral
Na₂A1₂Si₃0₁₀ . 2H₂O
Physical and optical properties :
- Colours : colourless to white, equally reddish , yellowish or greyish .
- Transparency : transparent to opaque
- Hardness : 5 to 5.5
- S.G. : 2.3 to 2.5
- R.I. 1.480 – 1.493
- Birefringence : 0.013
- Dispersion : 0.008
- Biaxial positive
- Pleochroism : -
- System orthorhombic
- Cleavage : perfect

NATROMICROLINE :
Synonym of Anorthose.

NATRONJADEIT :
Synonym of Jadeite.

NATRONORTHOKLAS :
German Synonym for Anorthose , designates equally an Orthose riche in sodium (Na).

NATROSPODUMENE :
Prohibited Appellation for a sunstone.

NATURAL GLASS :
See Obsidian, Moldavite, Tektite.

NAUSEANE :
Synonym of Nosean.

NECRONITE :
Variety of Orthose.

NEEDLE SPAR :
Old English name for Aragonite.

NEEDLE STONE :
English Name for sagenitic Quartz .

NEFELINA :
Synonym of nepheline.

NEOCHRYSOLITE :
Variety of Peridot containing manganese

NEOLITE :
Variety of Steatite.
or commercial name of an imitation of Turquoise, known also under the name of Turquoise of Hamburg.

NEOTOCITE :
Is an altered Rhodonite

NEOTURQUOISE :
Prohibited Appellation for a hydragilite. To the contrary of turquoise, this stone possesses a very good cleavage

NEPHELINE :
KNa₃(AlSiO₄)₄
Physical and optical properties :
- Colours : white, translucent grey, yellowish, brilliant green, reddish, blue-greenish or brown to brownish red
- Transparency : transparent to opaque
- Hardness : 5.5 to 6
- Density : 2.55 to 2.65
- R.I. : 1.532 - 1.536 to 1.544 - 1.549
- Birefringence : 0.004 - 0.005
- Dispersion : 0.008 to 0.009
- Uniaxial negative
- Pleochroïsm : none
- System : hexagonal

NEPHELITE :
Synonym of Nepheline. 

NEPHRITE or JADE-NEPHRITE:
Etym. From the Greek = Nephros : kidney; of which the stone sometimes has the form ; in the past times used as a remedy against diseases of the kidneys
One of the two minerals that are grouped together in gemmology under the name of jade
Mineralogically it is a mineral close to actinolite (from the family of the Amphiboles)
Silicate of calcium-magnesium-iron.
Micro-crystalline material. Occurs as an intergrown fine fibrous aggregate .
Ca₂(Mg,Fe)₅(Si₄O₁₁)₂(OH)₂
Physical and optical properties :
- colours : all colours possible; spinach green, green, greyish green, bluish green, reddish, brown, lavender, more rarely yellow or black; whitish to whitish grey is called ‘mutton fat jade’ in China.

The higher the content in iron, the darker in colour the mineral will be  .        
- Transparency : transparent to translucent, opaque ; uniform or spotted
- Hardness : 5.5 to 6.5
- Density : 2.90 to 3.10
- R.I. : 1.602 - 1.621 (± 0.003) ; ny : 1.609
- Birefringence : 0.019 to 0.021
- Dispersion : -
- Biaxial negative
- Pleochroism : none
– System : monoclinic

Inclusions :
Inclusions of graphite, limonite (=> nephrite with red reflections), magnetite (black), feldspar (whitish).

(AFRICAN) NEPHRITE :

Synonym of Transvaal Jade.
Prohibited Appellation ; it is a grossular garnet.

NEPHRITE of BOWEN :
Synonym of Bowenite.

NEPHRITE of KASTNER :
Synonym of Saponite.

NEPHRITE from TRANSVAAL :
Prohibited Appellation for a grossular garnet , equally called Transvaal Jade or African Nephrite

NEPHRITOID of BARSANOV :
Synonym of Bowenite.

NEPHRITOID of FROMME :
Variety of Tremolite.

NERCHINSK AQUAMARINE :
Prohibited Appellation for a topaze of aquamarine colour and coming from the district of Nerchinsk in Transbaikal region, Siberia

NEUROLITE :
Siliceous and fibrous variety of Agalmatolite.

NEVADA BLACK DIAMOND :
Prohibited Appellation for an obsidian.

NEVADA DIAMOND :
Prohibited Appellation for an artificially decoloured obsidian

NEVADA TOPAZ :
Prohibited Appellation for an obsidian having the colour of a smoky quartz.

NEW CALEDONIA JADE :
It is a Nephrite from Ouen Island, New Caledonia

NEW JADE :
Commercial name and Prohibited Appellation for a serpentine imitating jade
Hardness : 3 to 4
S.G. : 2.5 to 2.6

(NEW MINE) TURQUOISE:

Prohibited Appellation for odontolite .

NEW ZEALAND GREENSTONE :
Appellation given to a serpentine., originally this term designated nephrite .

NICCOLITE :
(Co,Ni)As₃
pale copper red in colour
Hardness : 5 to 5.5
S.G. : 7

NICOLO :
Variety of agate having a black or brown base and the upper part being bluish white
Used for making intaglios since Antiquity.

NICKELINE :
Synonym : Nyccolite.
Arsenate of nickel in which the cobalt can replace the nickel.
NiAs
Physical and optical properties :
- Colour : lead grey, greyish, sometimes pale copper red.
- Transparency : opaque
- Lustre : metallic
- Hardness : 4 to 5.5
- S.G. : 7.7 to 8.4
- system : hexagonal

NIERENSPECKSTEIN :
German term. Variety of Steatite.

NIERENSTEIN :
German Name for Nephrite.

NIGHT EMERALD :
Prohibited appellation for a yellowish peridot that appears lighter in colour under artificial light.

NIGRINE :
Black Variety of Rutile, iron containing, when polished, has the brilliance of a black diamond.

NILASA :
Burmese Term designating an inferior quality of Sapphire.

NILION :
Name used by the ancient Greeks for a hard stone, or a greyish or brown to honey coloured Jasper, or else a Nephrite.

NILKIESEL :
German Synonym for Egyptian Jasper .

NILT :
Burmese Name for big Sapphires.

NOBBIES :
Local Australian Term serving to designate a characteristic form of black Opal.

(NOBLE) OPAL :

Natural opal, designating generally all opals with a nice play of colour on a white to milky white background

NONTRONITE :
Variety of Chloropal.

NOSEAN or NOSEANE :
One of the stones of the group of Sodalite, properties resembling Sodalite or Lazurite.

NOSELITE :
Synonym of Nosean.

NOSIAN :

Original spelling of nosean .

NOUMEITE :
Synonym for Garnierite.

NOUVEAU JADE :
Prohibited Appellation French for New Jade designating Bowenite.

NOVACULITE :
It is a siliceous rock with a fine grain found at Hot Springs, Arkansas ; used as a stone to sharpen knives and sometimes facetted as a curio stone.

NUMEITE or NUMEAITE :
German Name for Noumeite.

NUNKIRCHEN JASPIS :
Jasper , grey to yellow or brownish red from Nunkirchen near Idar-Oberstein in Germany
Tinted in blue, it is sold under the term of German Lapis, or sometimes Swiss Lapis.

NUTTALLITE :
Variety of Scapolite.