Srilankite

Chemical formula: Ti⁴⁺O₂

Srilankite is a rare titanium and zirconium oxide, found as small, black, rounded grains in alluvium.

## Characteristics Srilankite is a rare mineral from the oxide group, chemically a complex titanium and zirconium oxide. It typically occurs as small, rounded grains or pebbles, up to several millimeters in size. Its crystals, though rarely observed in well-formed shapes, are tabular. It is usually opaque and has a black or blackish-brown color. ## Physical Properties This mineral is characterized by significant hardness, approximately 6.5 on the Mohs scale, which makes it scratch-resistant. Its density is relatively high, at 4.6 g/cm³. Srilankite's luster is described as metallic to submetallic. It is translucent to transparent in very thin fragments. ## Colors and Varieties Srilankite is a mineral with a uniform coloration. Its color ranges from black to blackish-brown. No color varieties or commercial varieties have been distinguished. ## History and Name Srilankite was first described in 1982 by A.M.R.G. Häfner, S.S. Hafner, E. Gnos, and T.G. Weerawarnakula. Its name comes from its discovery locality – Sri Lanka, where it was found in alluvial deposits in the Rakwana area. It is the type locality mineral for this country. ## Uses Due to its extreme rarity and small size of occurrences, srilankite has no industrial application. Its significance is purely scientific and collectible, being an object of interest for specialized collectors of rare minerals.

Properties

Mohs hardness
6.5
Luster
Metallic
Streak
Brownish-black
Density
4.6
Cleavage
not given
Fracture
Sub-Conchoidal
Transparency
Transparent,Translucent
Crystal system
Orthorhombic

Diagnostic features

## Identification Srilankite is identified by its black color, high hardness (6.5), relatively high density, and metallic luster. It occurs in the characteristic form of small, rounded grains in heavy mineral concentrates. ## Distinguishing from Similar Minerals It can be confused with other black, heavy minerals from alluvium, such as ilmenite, magnetite, rutile, or zircon. It is distinguished from ilmenite and magnetite by its lack of magnetic properties. Distinguishing it from rutile and zircon requires advanced analytical methods, such as chemical composition analysis (EDS/WDS) or X-ray diffraction (XRD), which will reveal srilankite's unique composition and crystal structure. ## Crystal Forms It is most commonly found as anhedral (irregular), rounded grains. Rarely, it forms poorly developed, tabular crystals in the orthorhombic system.

Geological environment

## Genesis Srilankite is a secondary mineral, found in alluvial deposits (river sediments). It forms as a result of weathering and erosion of parent rocks, followed by concentration in sediments due to its high density and chemical resistance. Its primary source (parent rock) is not precisely known, but it is presumed to be rocks rich in zircon and titanium. ## Mineral Associations In alluvial deposits, it co-occurs with other heavy minerals, such as zircon, ilmenite, geikielite, spinel, corundum (sapphire, ruby), and monazite. ## Localities The main and type locality for srilankite is the alluvial gem deposits in the Rakwana area, Ratnapura district, Sri Lanka. This is the only confirmed and well-documented locality for this mineral worldwide.

Rarity

Extremely rare

For collectors

## Quality Criteria As a microscopic and extremely rare mineral, the main criterion for collector value is the confirmation of its identity by analytical methods. "Loose" specimens are typically single, small grains. The most desirable are those embedded in epoxy resin (so-called "mounts") after microprobe analysis, with an accompanying printout confirming the chemical composition. Grain size, although usually not exceeding 1-2 mm, also affects value. ## Popular Localities The only source of collectible specimens is the type locality – alluvium in the Rakwana area of Sri Lanka. All specimens available on the market originate from this single location.

Care and storage

## Cleaning Srilankite specimens, typically small, resistant grains, can be cleaned in distilled water using a soft brush. An ultrasonic cleaner can also be used, but with caution. ## What to Avoid The mineral is chemically stable and hard, but contact with strong acids should be avoided. Despite its hardness, strong impacts can cause fractures. ## Storage Due to the small size of the grains, srilankite is best stored in special display boxes with compartments or in small, sealed containers to prevent loss. Protect from dust.

External references

Sources

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