Name/Title
Sal AmmoniacEntry/Object ID
2014.1.75Description
Chemical Composition: NH4Cl
Crystal System: Cubic or Isometric S
Description: Common Name: Sal Ammoniac
Chemistry: NH4Cl
Group: Halides
Location: Unknown
Description: A block of Sal Ammoniac, maybe from Mexico or Mt. Vesuvious. It has thin vertical layers with tabular cream colored rows of crystal. There are a couple of pieces of a brown
mineral or wood protruding from two surfaces.
Physical Charateristics:
Color is colorless, white or off-white almost yellow.
• Luster is vitreous.
• Transparency: Crystals are transparent to translucent.
• Crystal System: Isometric; possibly of the gyroidal class 4 3 2.
• Crystal Habits include cubes, octahedrons and dodecahedrons. Complicated arborescent, snowflake-like and dendritic specimens are available. Crusts and coatings are more common.
• Cleavage is poor in one direction.
• Fracture is conchoidal to earthy.
• Hardness is 1.5 - 2
• Specific Gravity is 1.5 (very light).
• Streak is white.
• Associated Minerals include sodium alum, sulfur and other fumarole minerals.
• Notable Occurrences include Tadzhikistan; Mt. Vesuvius, Italy and Paricutin Volcano, Michoacan, Mexico.
• Best Field Indicators are crystal habit, associations, origin of formation, softness and density.
Fracture: Conchoidal
Hardness: 2 Gypsum
Luster: Vitreous
Occurrence: Sal ammoniac forms on volcanic rocks near fume releasing vents. There is no liquid phase as the mineral crystallizes from these fumes in a process called sublimation. The crystallization occurs as the gases are escaping and crystals tend to be short-lived. Sal ammoniac is very soluble in water and crystals will be removed during the first rain of their existence, so to speak, if they are not removed by collectors first.
Other possible natural occurrences exist from underground burning coal seams. Alexander the Great is said to have found sal ammoniac crystals in a cave in a region that is now Tadzhikistan. The region was plagued by underground burning coal seams.
Sal ammoniac can be produced artificially and has its uses. When ammonia fumes are blown across hydrochloric acid; sal ammoniac fumes are produced. The technique is sometimes used to produce sal ammoniac coatings on dark objects that are about to be photographed. This will often enhance a difficult to photograph object by adding detail to the subject.
Natural crystals of sal ammoniac have an unreal or unnatural character to them. They are so small, delicate, intricate and at times quite beautiful that they just do not seem to be like other minerals. But it is sal ammoniac's natural methods of origin that lend themselves to produce these one-of-a-kind specimens.
Rock Type: Igneous
Specific Gravity: 1.5
Streak: WhiteCollection
RAGM Mineral CollectionAcquisition
Accession
2014.1Source or Donor
Crater Rock Museum (unknown donors)Acquisition Method
GiftDimensions
Width
3-3/4 inDepth
3-3/4 inLength
7-1/2 inLocation
Location
Display Case
FS-5-ARoom
Frieda Smith HallBuilding
Crater Rock MuseumCategory
ExhibitMoved By
Ian C.Date
January 29, 2025Notes
Major mineral groups installationLocation
Shelf
CS-D-7Room
Curation StorageBuilding
Crater Rock MuseumCategory
StorageMoved By
CuratorDate
February 21, 2024