Mineral description : Laumontite

Lots of white laumontite crystals on calcite crystals. From Nannestad, Norway.
An aggregate of laumontite crystals from Iveland, Norway.
Stained by rust. Another laumontite crystals from Iveland, Norway.
This time a single crystal on feldspar. Note the steep termination.

Mineral class Silicates : Tectosilicates : Zeolite group.

Chemical formula CaAl₂Si₄O₁₂^.4H₂O

Crystal system Monoclinic

Habitus As square prismatic crystals with steep oblique terminations. As fibric radiating aggregates or massive.

Cleavage Perfect, fracture uneven, brittle.

Hardness 3.5 - 4

Density 2.2 - 2.3

Color White, yellow, pinkish, brownish.

Streak White.

Luster Vitreous to pearly on cleavages, transparent to translucent.

Description

Occurance Created by hydrothermal processes in cavities in igneous rocks. In sedimentary beds as a decomposition of analcime or as metamorphose of plagioclase.

Associates Other zeolites, apophyllite, datolite, calcite, chlorite.

Notes Named after Francois Pierre Nicolas Gillet de Laumont who discovered laumontite in .....
Slowly looses water in dry atmosphere and turns in a white powder, . To preserve specimens they have to be kept it an airtight container.
Soluble in hydrocloric acid under gelatinization.

Localities Not the most common zeolite but a number of localities exists.
Sweden : Rare in Sweden.

Kleva and Ädelfors mines, Småland. As fibric aggregates in fractures in calcite.
Lindström mine, Skellefteå mining field, Västerbotten. As small prismatic crystals.
Väddö, Uppland. As compact pinkish aggregates in bedrock fractures.

Norway :

In a quarry near Horten.
Kongsberg silver mine. Found on harmotome. Common in the silver ore veins.
Eiang (=Haukom) mine, Telemarken. In small cavities.
Landsverk 1, Evje.
Åserud iron mine. In fractures in diabase.
Sulitjelma. Together with other zeolites associated with pyrite occurances.
Honningsvåg, Magerøy, Finnmark.
Ågskardet (sic). In the pegmatite.

Finland : (Sorry if the names are messed up, but I don't speak Finnish)

Arajärvi, Hauho.
Porrasniemi, Lammi.
Paukkajanvaura, Enon.
Piukkala, Paraisten.
Nevaksen, Sipoo. In limestone.
Viitasaari. In hydrothermal transformed gneiss.

To silicate index.
Mineral group index.
Main index.

If you have some questions, suggestions or comments you are welcome to write me a line or two.

axelsson@acc.umu.se

To my homepage.
Last changed : 2001-07-09

Mineral class	Silicates : Tectosilicates : Zeolite group.
Chemical formula	CaAl₂Si₄O₁₂^.4H₂O
Crystal system	Monoclinic
Habitus	As square prismatic crystals with steep oblique terminations. As fibric radiating aggregates or massive.
Cleavage	Perfect, fracture uneven, brittle.
Hardness	3.5 - 4
Density	2.2 - 2.3
Color	White, yellow, pinkish, brownish.
Streak	White.
Luster	Vitreous to pearly on cleavages, transparent to translucent.
Description
Occurance	Created by hydrothermal processes in cavities in igneous rocks. In sedimentary beds as a decomposition of analcime or as metamorphose of plagioclase.
Associates	Other zeolites, apophyllite, datolite, calcite, chlorite.
Notes	Named after Francois Pierre Nicolas Gillet de Laumont who discovered laumontite in ..... Slowly looses water in dry atmosphere and turns in a white powder, . To preserve specimens they have to be kept it an airtight container. Soluble in hydrocloric acid under gelatinization.
Localities	Not the most common zeolite but a number of localities exists. Sweden : Rare in Sweden. Kleva and Ädelfors mines, Småland. As fibric aggregates in fractures in calcite. Lindström mine, Skellefteå mining field, Västerbotten. As small prismatic crystals. Väddö, Uppland. As compact pinkish aggregates in bedrock fractures. Norway : In a quarry near Horten. Kongsberg silver mine. Found on harmotome. Common in the silver ore veins. Eiang (=Haukom) mine, Telemarken. In small cavities. Landsverk 1, Evje. Åserud iron mine. In fractures in diabase. Sulitjelma. Together with other zeolites associated with pyrite occurances. Honningsvåg, Magerøy, Finnmark. Ågskardet (sic). In the pegmatite. Finland : (Sorry if the names are messed up, but I don't speak Finnish) Arajärvi, Hauho. Porrasniemi, Lammi. Paukkajanvaura, Enon. Piukkala, Paraisten. Nevaksen, Sipoo. In limestone. Viitasaari. In hydrothermal transformed gneiss.