Minguzzite
Chemical formula: K<sub>3</sub>Fe<sup>3+</sup>((C<sub>2</sub>)<sup>6+</sup>O<sub>4</sub>)<sub>3</sub>·3H<sub>2</sub>O
Minguzzite is a very rare mineral from the oxalate group, forming small, prismatic crystals of an intensely green color.
Properties
- Mohs hardness
- 2.5
- Luster
- Vitreous
- Streak
- Pale green
- Density
- 2.16
- Cleavage
- Perfect on {010}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Characteristic features of minguzzite include its intense green color, vitreous luster, and occurrence as small, acicular or prismatic crystals. A key diagnostic feature is its solubility in water, although this is a destructive test. It also reacts with acids. ## Distinguishing from Similar Minerals Due to its unique occurrence environment (associated with guano) and characteristic appearance, it is difficult to confuse with other minerals. Other secondary green copper or iron minerals (e.g., annabergite, brochantite) have different physical properties (they are harder, do not dissolve in water) and occur in different parageneses. ## Crystal Forms Minguzzite forms elongated, prismatic crystals, often acicular in habit. They typically occur as radial or tangled aggregates, as well as coatings and crusts on the host rock.
Geological environment
## Genesis Minguzzite is a mineral of organic origin, forming under very specific conditions. It forms as a product of the reaction of solutions derived from the decomposition of bat guano with iron minerals present in rocks. It is a secondary mineral, crystallizing in the dry climate of caves or on rock outcrops. ## Mineral Associations In its type locality (Elba Island), minguzzite co-occurs with hematite, goethite, pyrite, gypsum, and other rare oxalates, such as humboldtine and oxalite (formerly known as whewellite). ## Localities The most important and type locality for minguzzite is the Rio Marina cave on Elba Island, Italy. This is the only confirmed and well-documented locality for this mineral in the world, making it endemic to this location.
Rarity
Extremely rare
For collectors
## Quality Criteria The quality of a minguzzite specimen is primarily assessed based on the abundance and development of its crystals. Most valued are specimens with visible, well-formed, prismatic crystals of intense, emerald-green color, forming rich aggregates on a small rock matrix. Contrast with a hematitic or limonitic host rock also enhances visual appeal. ## Popular Localities The only source of collector specimens is the historical type locality – Rio Marina on Elba, Italy. Material from this location is extremely rare and sought after by collectors specializing in systematics or minerals from specific localities (so-called "locality collectors").
Care and storage
## Cleaning Minguzzite specimens are extremely delicate and sensitive to water. Mechanical cleaning is highly risky. If necessary, compressed air (from a safe distance) can be used to remove loose dust particles. Any contact with liquids must be avoided. ## What to Avoid The mineral is soluble in water, so contact with water, moisture, and chemical solutions must be strictly avoided. As a very soft mineral, it is susceptible to scratches and mechanical damage. It should be protected from high temperatures and direct sunlight, which can lead to its dehydration and destruction. ## Storage It is recommended to store minguzzite specimens in sealed, dry containers (e.g., "perky boxes") away from sources of moisture and light. It is best to keep it in stable temperature conditions to prevent degradation. Due to its brittleness, it should not come into contact with other minerals.