Fossil and Petrology collections, New South Wales The Petrology Collection contains 70,000 rocks and thin sections. It was started in the 1870s as two separate collections, one with 9,000 rocks and the other with 43000 thin sections. Hand written catalogues exist for each. After 1912, only one collection was continued up to the present day. The two old subcollections have much more significance than their sizes would indicate, because much of the material comes from old mine sites, and many of these are no longer available for sampling. Furthermore a few samples, have world significance, such as the thin section from the very sample of Copeton dolerite
Experimental petrology are analyzed - qualities of interest include mineral assemblage (which minerals crystallized and how much), mineral chemistry, and liquid (the remainder of the synthetic magma base) composition. Equilibrium crystallization studies are those in which a starting liquid is cooled until fully crystalline. This is taken to be the "equilibrium state" of the composition under those particular P/T conditions. Criticisms of equilibrium crystallization include the observation that real-world systems are believed to rarely sit still during crystallization and thus would not be able to properly equilibrate. Fractional crystallization studies represent a fairly recent trend in experimental petrology, gaining popularity as a