Spadaite

Chemical formula: MgSiO₂(OH)₂·H₂O

A rare, hydrated magnesium silicate, forming amorphous masses with a resinous luster, found in weathering products of other magnesium minerals.

## Characteristics Spadaite is an amorphous, hydrated magnesium silicate, meaning it does not form regular crystals. It occurs as masses, aggregates, or as an alteration product of other minerals. Its appearance is usually inconspicuous, and specimens have a characteristic resinous to greasy luster. It is a soft and light mineral. ## Physical Properties The hardness of spadaite on the Mohs scale is 2.5, making it a soft mineral that can be scratched with a fingernail. It has a low specific gravity, approximately 2.13 g/cm³. It is translucent to subtranslucent. It does not exhibit cleavage, and its fracture is uneven. ## Colors and Varieties Spadaite most commonly ranges in color from reddish, through yellowish, to white. The coloration is often non-uniform. There are no named varieties of this mineral. ## History and Name The mineral was named in 1846 in honor of Lavinio de' Medici Spada (1801-1863), an Italian naturalist and politician who first drew attention to this material. It was described by the German mineralogist Johann Friedrich August Breithaupt. The type locality (locus typicus) is Capo di Bove in Italy. ## Uses Spadaite has no industrial application. Its significance is purely scientific and as a collector's item, as a rare secondary mineral.

Properties

Mohs hardness: 2.5
Luster: Resinous
Streak: White
Density: 2.13
Fracture: Uneven
Transparency: Translucent

Diagnostic features

## Identification Spadaite is identified by its amorphous form, resinous luster, low hardness (2.5 on the Mohs scale), and characteristic reddish or yellowish coloration. It occurs as an alteration product of other magnesium minerals, often in rock cavities. ## Distinguishing from Similar Minerals It can be confused with other amorphous silicates or weathering products. It differs from opal by its lower hardness and different geological context. From talc, to which it is chemically related, it differs by the absence of talc's characteristic silky or pearly surface and greasy feel to the touch. ## Crystal Forms As an amorphous substance, spadaite does not form crystals. It occurs as compact, earthy, or reniform masses and aggregates.

Geological environment

## Genesis Spadaite is a secondary mineral. It forms as a result of hydrothermal alteration or weathering of other magnesium-rich minerals, such as perovskite, in volcanic rocks. It forms at low temperatures, filling voids and fissures in the host rock. ## Mineral Associations It often co-occurs with minerals from which it forms or in whose company it is created. Typical associated minerals include calcite, hematite, magnetite, augite, leucite, and various minerals from the serpentine group. ## Localities The most important and classic locality, which is also the type locality, is Capo di Bove in the Lazio region of Italy. Other known localities include the Crestmore mine in California (USA) and some occurrences in Germany (Eifel) and Scotland.

Rarity

Very rare

For collectors

## Quality Criteria The collector's appeal of spadaite is limited due to its inconspicuous appearance. The most valued specimens are those rich in material, with intense, reddish coloration and a distinct resinous luster. A well-documented locality is also important, especially if it is the type locality (Capo di Bove). ## Popular Localities Material from the classic, historical locality of Capo di Bove in Italy is by far the most desired by collectors. Specimens from other locations, such as the Crestmore mine in the USA, also have value for collectors specializing in rare minerals or minerals from a specific locality.

Care and storage

## Cleaning Spadaite specimens should be cleaned very carefully, using a soft brush to remove dust. Due to its softness and potential reactivity, avoid washing in water, and especially avoid using any detergents. ## What to Avoid Avoid contact with water and chemicals, which can alter its structure. As an amorphous and hydrated mineral, it is sensitive to high temperatures, which can cause dehydration and disintegration. Protect it from scratching by harder minerals. ## Storage Spadaite specimens are best stored in separate, padded boxes or display cases to prevent abrasion and mechanical damage. They should be kept in a dry place, away from direct sunlight and heat sources.

Sources

IMA Mineral List (CNMNC)