Kyanite is an aluminum silicate mineral notable for pronounced hardness anisotropy and blue pleochroic colour.

Labradorite is a plagioclase feldspar known for labradorescence caused by light interference in lamellar structures.

Laguna agate is a prized Mexican agate known for tight, colorful fortification banding.

Lapis lazuli is a lazurite-rich metamorphic rock used as a gemstone and ornamental material.

The character of Larimar comes through in its aqua, blue, cyan / blue-green, green, and brown colour and the way that colour interacts with a silicate structure. That combination of aqua body colour, 6.5 Mohs hardness, and vitreous lustre is what usually makes it recognisable in practice. The secondary blue note often matters more than people expect when separating it from lookalikes.

Lava stone is a porous volcanic basalt used as an ornamental bead and decorative material.

Lazurite is a blue feldspathoid mineral and the key color component in lapis lazuli.

Lemon quartz is a trade name for bright yellow quartz, commonly achieved through irradiation and/or heat treatment.

Lemurian quartz is a trade term for naturally striated quartz crystals, not a distinct mineral species.

Libyan desert glass is a natural silica glass from the Sahara, widely considered impact-related in origin.

Liddicoatite is a calcium-rich tourmaline species known for striking multicolor zoning patterns.

Durability is part of the appeal of London Blue Topaz, not merely a technical footnote. Jewellers who need dependable wear resistance often come to it for different reasons, but identification still comes back to blue body colour, 8 Mohs hardness, and vitreous lustre.

Mahogany obsidian is an obsidian variety showing reddish-brown mottling from iron-rich inclusions.

Malachite is an opaque copper carbonate mineral recognized by vivid green banding.

Locality plays an important role in how Maxixe is understood in the gem trade. Collectors and lapidaries comparing similar stones often come to it for different reasons, but identification still comes back to blue body colour, 7.5 Mohs hardness, and vitreous lustre. The secondary green note often matters more than people expect when separating it from lookalikes.

Melanite is a black titanium-rich variety of andradite garnet.

Meteorite stone is a trade category for extraterrestrial material used in jewelry and collector pieces.

Mettle stone is handled as a trade-name decorative material requiring supplier-level composition disclosure.

Mexican Opal profile is under factual gemological review. Properties shown here are provisional unless marked as verified.

Moldavite is a natural impact glass (tektite) formed during the Ries impact event and found in Central Europe.

Moonstone is recognised by light that seems to float just beneath the surface. That soft billowing glow gives even simple cabochons an internal life that is very different from the brilliance expected in faceted transparent gems.

Morganite profile is under factual gemological review. Properties shown here are provisional unless marked as verified.

Moss agate is chalcedony containing green mineral inclusions that resemble moss or vegetation.

Moss chalcedony is a chalcedony variety featuring natural dendritic or mossy internal inclusions.