Australian Diamond Mining

Are you a fellow diamond enthusiast? If so I would like to share some of my aesthetic pleasure derived from this beautiful gemstone. My approach is that of a geo-scientist working as a consultant to the gemstone industry, especially the Diamond Exchange.

My in-line to diamonds is via their crystallography – beautiful natural shapes reflecting their formation, provenance and tortuous history in volcanic systems.

Like snowflakes, no two crystals are ever the same. – Unique expressions of natural artistry.

Crystallography of Diamonds from Eastern Australia

Classification

Primary Forms

Resorbed Forms

Etching

Twins

C: Cube

D: Dodecahedron

F: Tetrahedron

O: Octahedron

/ Combination

HC: Tetra hexahedron

HD: Pseudo dido decahedron

HF: Hex tetrahedron

HO: Hex octahedron

TD: Pseudo dodecahedron

TO: Trisoctahedron

-c cubic

-hc tetrahexahedral

-o octahedral

-to trisoctahedral

2 x

5 x

In Eastern Australia we have a great geological mystery, shared by Alaska, California, Kamchatka, Burma, Thailand and the Urals: Theoretically diamonds should not be concentrated in the “blind placers” of such places. Most diamonds apparently come from stable ancient crust areas – cratons, beneath which the rocks are relatively cool, within the stability field for diamond. Being meta-stable, diamond readily converts to graphite or just burns to carbon dioxide unless stringent protection can be afforded. High temperatures cause destruction of diamond if upward transport is too slow, releasing pressure without appropriate cooling rates.

Eastern Australia presents a puzzling situation where certain local areas yield abundant diamonds, at least 500,000 carats from the Copeton and Bingara Fields of Northern New South Wales alone. Prior to production from Argyle , Western Australia this was the only commercial production in Australia. But ; one big problem: The NSW diamonds occur over 1000 km from the nearest craton, straddling a geothermally hot “mobile belt” left over from a major mountain – building episode (orogeny) from some 400 to 200 million years ago. This does not appear to be a suitable place to find a primary diamond-bearing volcanic system! But; how does one explain local concentrations and peculiarities of form characterising each find?

Long distance alluvial travel or ice carting dilute and scatter diamonds to uneconomic grades.

C: Cubes

HC-o

C/D-o

TD-o

TWIN:

2X TD-c

F: Tetrahedra

D: Dodecahedra

HF-hc

No primary forms confirmed

C/D, C/O, C/D/O

Combinations not recorded