Labradorite is an unusual mineral. It can display a beautiful iridescent play of colo... More
Labradorite is an unusual mineral. It can display a beautiful iridescent play of colors, caused by internal fractures in the mineral that reflect light back and forth, dispersing it into different colors. This effect, known as labradorescence, gives Labradorite its appeal and fame. Specimens sold to collectors are usually polished or sliced by dealers to fully bring out this effect. Sliced slabs are sometimes sold by dealers in water, which enhances the effect. Labradorite belongs to the Plagioclase Feldspar group, an
isomorphous solid solution series. Albite is one member,
containing sodium and no calcium. The other end member, Anorthite,
contains calcium and no sodium. Labradorite is an intermediary
member of this series. Labradorite is considered by some authorities as a
variety of Anorthite rather then a separate mineral. The acclaimed
Dana's System of
Mineralogy lists Labradorite as an individual mineral,
whereas the IMA does not recognize it as individual mineral
species, but rather a sodium-rich variety of Anorthite. For additional information, see the gemstone section on Labradorite. Hide
|
Laumontite is a member of the zeolite group , and occurs in many of the zeolite depos... More
Laumontite is a member of the zeolite group, and occurs in many of the zeolite deposits. It is not a stable mineral, losing water in its structure upon exposure to air. This causes Laumontite to be white and powdery, and will cause specimens to crumble when touched. Large crystals can be preserved by coating it with a plastic waterproof sealant. Laumontite was named after Gillet de Laumont (1747-1834), a French mineralogist and hunter credited with discovering this mineral in Brittany, France in 1785. Hide
|
div Lawsonite is a rare mineral, and is a hydrated variant of the feldspar Anorthite ... More
Lawsonite is a rare mineral, and is a hydrated variant of the feldspar Anorthite. It is named after Andrew Cowper Lawson (1861-1952), a professor of geology at the University of California at Berkeley. The Bay Area of California is the type locality and primary region of this mineral, and this is where Lawson taught. Lawson's main claim to fame is his identification and naming of the San Andreas Fault.
|
Lazulite is an aesthetic blue mineral that forms in distinct crystals. Its name is ve... More
Lazulite is an aesthetic blue mineral that forms in distinct crystals. Its name is very similar and often confused with Lazurite, which is an entirely different mineral species. However, the names of both these minerals are derived from the term "Lazaward", which means heaven in Arabic, alluding to their blue color. Lazulite forms a series with the rare mineral Scorzalite, which is the iron-rich equivalent of Lazulite. Hide
|
Lazurite is famous for its gem form, Lapis Lazuli . Lapis Lazuli, casually called by ... More
Lazurite is famous for its gem form, Lapis Lazuli. Lapis Lazuli, casually called by its shortened name Lapis, is the gemstone form of Lazurite that is associated with white Calcite and sparkling Pyrite. The name Lazurite is derived from the term "Lazaward", which means heaven in Arabic, alluding to its blue color. Lazurite occurs almost exclusively in massive form without any visible crystals. The exception is the historic occurrence of Afghanistan, where this mineral is famous and highly regarded for producing outstanding rich-blue crystals unlike any other minerals. These crystals, almost always perched in a white marble matrix, are highly sought out after by mineral collectors. When not used as gemstones, the non-crystallized forms are often polished for collectors and may also be sliced into slabs.
Lazurite forms a solid solution series with Hauyne, essentially sharing the same chemical formula but with a variation of the sulfide over the sulfate. Lazurite has the sulfide dominating, whereas Hauyne has the sulfate dominating. Much of the known Lazurite material is actually sulfate-dominating, which means it is in fact Hauyne and not Lazurite. This is especially true at the most famous locality of Lazurite at Sar-e-Sang in the Kokcha Valley of Afghanistan, where all the Lazurite has in fact been determined to be Hauyne. Despite this, the mineral community still accepts this material as Lazurite despite the scientific inaccuracy. It has become accepted to refer to the opaque, non- fluorescent, ultramarine-blue material as Lazurite, and all other material, especially when exhibiting transparency, as Hauyne.
|
Lead is a common element , but is very rare in a native state. Some locations contain... More
Lead is a common element, but is very rare in a native state. Some locations contain lead as a by-product of smelting operations, where masses of lead are formed, but they are not naturally occurring. Such specimens are occasionally sold to collectors. Hide
|
Lepidolite is a lithium rich mica known for its pink and lilac colors. It is a common... More
Lepidolite is a lithium-rich mica known for its pink and lilac colors. It is a common matrix mineral to Tourmaline and Quartz, providing them with a very aesthetic and glittery base. A pink variety of the related mica mineral Muscovite can be identical in appearance to Lepidolite, and is many times incorrectly labeled as Lepidolite. Hide
|
Leucite is a member of the feldspathoid group , forming directly from cooling lava in... More
|
Liddicoatite is an uncommon form of Tourmaline , almost identical in chemical composi... More
Liddicoatite is an uncommon form of Tourmaline, almost identical in chemical composition to Elbaite, but with a calcium atom replacing a sodium atom in its chemical formula. Liddicoatite was not recognized as a separate Tourmaline species until 1977. Prior to that time, it was thought to be Elbaite. The original discovery of Liddicoatite in Madagascar was believed to be fully dominating in hydroxyl in its chemical formula. Subsequent analysis has determined a fluorine presence in place of some of the hydroxyl, though several localities (though not the type locality) do in fact contain all hydroxyl and no fluorine. The fluorine-rich Liddicoatite is recognized as a distinct mineral species by the IMA, and termed Fluor-liddicoatite. Liddicoatite is name after Richard T. Liddicoat (1918-2002), a well-known gemologist who was the president of the GIA, and inventor of the Diamond grading system. Hide
|
Limonite is scientifically not considered a true mineral as it lacks a definitive che... More
Limonite is scientifically not considered a true mineral as it lacks a definitive chemical formula and crystal structure. However, all mineral reference guides list it together with other minerals. Limonite is a matrix base of many other minerals, and the term gossan is used as a reference to Limonite when it is used as a a matrix for another mineral or has formed an undesirable staining on top of it. Limonite is extremely common and forms the coloring matter in many soils. It is also responsible for the coloring on the weathered surfaces of rocks. Much Limonite, especially the fibrous type, is either Goethite or altered Goethite that absorbed water in its chemical structure. Limonite commonly forms as a pseudomorph over other minerals, especially Pyrite, Marcasite and Siderite. These pseudomorphs are very identifiable by their partial rusting look and yellow staining. Hide
|
Linarite is known for its exceptionally bright blue color. Specimens may be mistakenl... More
Linarite is known for its exceptionally bright blue color. Specimens may be mistakenly labeled as Azurite, since both are found in the same localities and can be very similar in appearance. Simple tests can distinguish the two, for their physical properties differ.
Linarite is named for its type locality, Linares, in the Andalusian province of Jaén, Spain. Hide
|
div Lithiophilite is an end member of the Triphylite series , with Lithiophilite bein... More
Lithiophilite is an end member of the Triphylite series, with Lithiophilite being the manganese-rich end member, and Triphylite being the iron-rich end member. Lithiophilite and Triphylite both commonly alter to secondary phosphates such as Vivianite, as well as to manganese and iron oxides.
Lithiophilite was named for its lithium content ("lithio"), and the Greek term, "philos", meaning friend, alluding to its composition of lithium as an integral component of its structure. Hide
|
Loellingite, also known as L llingite, is named after the Austrian type locality it w... More
Loellingite, also known as Löllingite, is named after the Austrian type locality it was first described in, which is Loelling (or Lölling), Carinthia, Austria. Since the English language lacks the letter O with an umlaut, this guide uses the alternate spelling of Loellingite.
Loellingite belongs to the Loellingite group, which is a group of chemically related isomorphous minerals that are all uncommon. Other members discussed in this guide are Rammelsbergite and Safflorite.
|
div Luzonite is a rare mineral that is dimorphous with Enargite . Luzonite forms in t... More
Luzonite is named after its occurrence in Mancayan, Luzon Island, in the Philippines, which is the type locality for this mineral.
|
