Anthracite and it is found most abundantly in areas that have been subjected to considerable stresses and pressures, such as the flanks of great mountain ranges. Anthracite is associated with strongly deformed sedimentary rocks that were subjected to higher pressures and temperatures (but short of metamorphic conditions) just as bituminous coal is generally associated with less deformed or flat-lying sedimentary rocks. For example, the compressed layers of anthracite that are deep mined in the folded Ridge and Valley Province of the Appalachian Mountains of the Coal Region of East-central Pennsylvania are extensions of the same layers of bituminous coal that are
Anthracite budgerigar mutation the Anthracite locus. This darkens the body colour to a shade somewhat deeper than a Dark Green. The DF Anthracite Light Green, with two Anthracite alleles, is a deep olive colour. In the blue series varieties the SF Anthracite Skyblue has one Anthracite allele and one wild-type allele, with a body colour rather like a deep Cobalt. The DF Anthracite Skyblue with two Anthracite alleles, the true Anthracite variety, has a dark grey, almost black, body colour with mauve overtones. Because the Anthracite factor is always visibly expressed no budgerigar can be split for Anthracite. The heterozygotes of Anthracite with