Matlockite is a rare lead

Lead

Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

 halide mineral

Halide mineral

The halide mineral class include those minerals with a dominant halide anion . Complex halide minerals may also have polyatomic anions in addition to or that include halides.Examples include the following:*Halite NaCl*Sylvite KCl...

, named after the town of Matlock in Derbyshire

Derbyshire

Derbyshire is a county in the East Midlands of England. A substantial portion of the Peak District National Park lies within Derbyshire. The northern part of Derbyshire overlaps with the Pennines, a famous chain of hills and mountains. The county contains within its boundary of approx...

, England

England

England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

, where it was first discovered in a nearby mine. Matlockite (chemical formula: PbFCl) gives its name to the matlockite group which consists of rare minerals of a similar structure.

Description

The mineral, a lead fluorochloride (formula PbFCl), was discovered sometime around the early 1800s at Bage Mine at Bolehill

Bolehill, Derbyshire

Bolehill is an area of Wirksworth, Derbyshire, England. It is located in the north of the town and has connections to the lead mining industry. Originally a village in its own right, Bolehill became part of the outskirts of Wirksworth upon the town's expansion during the 19th and 20th...

 near Matlock, together with specimens of phosgenite

Phosgenite

Phosgenite is a rare mineral consisting of lead chlorocarbonate, 2CO3. The tetragonal crystals are prismatic or tabular in habit: they are usually colorless and transparent, and have a brilliant adamantine lustre. Sometimes the crystals have a curious helical twist about the tetrad or principal...

 and anglesite

Anglesite

Anglesite is a lead sulfate mineral with the chemical formula PbSO4. It occurs as an oxidation product of primary lead sulfide ore, galena. Anglesite occurs as prismatic orthorhombic crystals and earthy masses, and is isomorphous with barite and celestine. It contains 74% of lead by mass and...

. Although phosgenite was known at this time, it seems likely that matlockite itself remained unappreciated as a new mineral for some fifty years. It was given the name by Greg in 1851. The first mention of Matlockite may have been in Mawe's

John Mawe

John Mawe was a British mineralogist who became well known for his practical approach to the discipline.-Biography:Mawe was born in Derby in 1764 to Samuel Maw. His mother died when he was ten and he was raised by his father's second wife, Francis . In early life he appears to have spent fifteen...

 Mineralogy of Derbyshire in 1802 in which he gives a detailed description of phosgenite, which is then followed by a mention of a mineral he refers to as "glass lead" - a description which does rather equate to the appearance of matlockite. It is a light, translucent creamy-yellow colour, but heavy in weight having a density that is over 7.1.

A very large specimen 10cm across, and originating from Derbyshire, exists in the collections of the American Museum of Natural History

American Museum of Natural History

The American Museum of Natural History , located on the Upper West Side of Manhattan in New York City, United States, is one of the largest and most celebrated museums in the world...

. A 7cm specimen can be found in the collection of Derby Museum and Art Gallery

Derby Museum and Art Gallery

Derby Museum and Art Gallery was established in 1879, along with Derby Central Library, in a new building designed by Richard Knill Freeman and given to Derby by Michael Thomas Bass. The collection includes a whole gallery displaying the paintings of Joseph Wright of Derby; there is also a large...

.

Matlockite has been reported from a variety of locations since its discovery at the type locality

Type locality (geology)

Type locality , also called type area or type locale, is the where a particular rock type, stratigraphic unit, fossil or mineral species is first identified....

 of Derbyshire. The mineral is also found in Tiger

Tiger, Arizona

Tiger is a ghost town in Pinal County in the U.S. state of Arizona. The town was settled as Schultz around 1881 in what was then the Arizona Territory, then later reestablished as Tiger after World War I.-History:...

, Arizona

Arizona

Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...

, Laurium

Laurium

Laurium or Lavrio is a town in southeastern part of Attica, Greece. It is the seat of the municipality of Lavreotiki...

 in Greece

Greece

Greece , officially the Hellenic Republic , and historically Hellas or the Republic of Greece in English, is a country in southeastern Europe....

, a mine near Essen

Essen

- Origin of the name :In German-speaking countries, the name of the city Essen often causes confusion as to its origins, because it is commonly known as the German infinitive of the verb for the act of eating, and/or the German noun for food. Although scholars still dispute the interpretation of...

 in Germany

Germany

Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 and near Campiglia in Tuscany

Tuscany

Tuscany is a region in Italy. It has an area of about 23,000 square kilometres and a population of about 3.75 million inhabitants. The regional capital is Florence ....

. Samples have also been found at locations in South Africa, Peru, Chile, Australia, Austria, France and Italy.

The matlockite group

The matlockite group consists of a number of minerals which share a similar crystal structure. The group includes bismuth, lead or calcium halides: bismoclite (BiO)Cl, daubréeite (BiO)(OH,Cl), laurionite

Laurionite

Laurionaite is a halide mineral, named after the town Laurium in Greece. Laurionite can also be produced by lead oxide in a salt solution....

 PbCl(OH), paralaurionite PbCl(OH), rorisite CaFCl, zavaritskite (BiO)F and the eponymous matlockite.