Palygorskite, also known as attapulgite, is an odd mineral. It forms
matted felted masses that closely resemble woven cloth. In fact, an informal
name for this natural fabric is "Mountain Leather" and
appears with attached calcite
crystals that look like interwoven glass beads.
Palygorskite is often classified as a clay
mineral because it is present in some soils and behaves like many other
clay minerals. Unlike most other clay minerals, palygorskite can form large
crystals. Palygorskite is found in hydrothermal deposits, soils and along
faults often lining the slicken sides of fault lines.
- Color is white, gray pale lavender.
- Luster is silky to dull.
- Transparency: Crystals are transparent to translucent.
- Crystal System is monoclinic; 2/m
- Crystal Habits include fibrous felted masses termed "Mountain
Leather" as well as disseminated grains and platy crystals.
- Cleavage is perfect in one direction producing thin sheets or
- Fracture is not readily observed due to cleavage, but is uneven.
- Hardness is less than 2.
- Specific Gravity is approximately 2.2+ (well below average)
- Streak is white.
- Other Characteristics: Thin crystal sheets are flexible.
- Associated Minerals include calcite,
- Notable Occurrences include Pend Oreille Mine, Metaline Falls,
Washington (good "Mountain Leather" source) and Arizona,
USA; Morocco; Molotov Mining District of the Ural Mountains in Russia and
the Shetland Islands.
- Best Field Indicators are crystal habit, flexible sheets, environments