#supergene

Goethite pseudomorph after Pyrite

Brochantite star

Many of us have grown similar crystals by hanging a piece of string into a copper sulphate solution and letting it evaporate. In nature, an arid climate or an oxidising (see http://bit.ly/1I4XWKt for an explanation) primary copper sulphide deposit is required for this mineral to form. Colour ranges from bright emerald green to blue green, though its softness (3.5 on Mohs scale) prevents faceting or jewellery use.

Since it forms in the same environments as malachite and azurite (copper carbonates), they are frequently found together, and sometime brochantite replaces the other minerals, taking on their crystal shape in a process called pseudomorphism (from pretend shape in Greek). The more usual distinguishing shape is as sprays of acicular (needle shaped) crystals, often radiating from a common centre. It go was named in 1824 after a French mineralogist, Brochant de Villiers and is an important ore mineral.

Main localities include the copper mines of the Atacama in Chile, the Zaire copper belt in the Democratic Republic of Congo, the Tsumeb mine (see http://bit.ly/1c2CjkD) and Arizona in the USA. A few stunning specimens (including the 2.5 x 2.5 x 1.8 cm one in the photo) have recently emerged from the Milpillas mine in Sonora, Mexico.

Loz

Image credit: Spirifer Minerals

For years, insect lovers have known that some swallowtail butterfly species — such as Pachliopta aristolochiae — make toxins to dissuade predators. Other swallowtails, such as Papilio polytes females, are masqueraders — they lack toxins, but mimic coloration and patterns of their poisonous kin to avoid getting munched on by birds, spiders or lizards.

But how?

A study published Tuesday traces this trait — called supergene mimicry — to a single ancestor who lived two million years ago. The gene experienced a chance mutation, whereby a section of the chromosome housing the doublesex gene had randomly flipped.

The scientists traced the lineage of this mutation in five species and several variations of female swallowtails. As with many mutations, one would think that the butterflies with the out-of-order genes would soon die off. But the team said natural selection maintained the flipped gene because it gave rise to the butterflies ability to mimic toxic butterflies.

Since butterflies go through about eight generations a year, that’s millions and millions of generations to hone this trait, or in some cases, lose it if another mutation comes along. Today, the distribution of these mimics spans butterflies from central Asia to eastern Australia.

Green Blue Breccia

A breccia is a rock with large, angular clasts, held together by a cement. The cement in this rock is made of the spectacularly colored copper minerals azurite and malachite. The blue mineral is azurite, while the green mineral is malachite. The two minerals have copper in slightly different bonding environments for copper, so they absorb light at different wavelengths.

Both azurite and malachite are carbonate minerals. When copper starts in the ground, it can dissolve in the weak acid that is rainwater. That copper then moves downwards with the rainwater and reprecipitates as azurite and malachite cements once the acidity is used up at depth. This type of concentrated ore deposit, formed by precipitation from rainwater, is called a “Supergene” deposit.

This rock comes from the Phelps Dodge Morenci Mine near Morenci, Arizona. The full polished slab is 8.1 cm across.

-JBB

Image credit: https://flic.kr/p/oKWf5t

What a stunner Measuring 22.6 x 12.6 x 5.6 cm and mined in China we have here an amazing example of a stalactite of the copper carbonate mineral Malachite consisting of nested tapering spires displaying the satiny lustre for which this fibrous mineral is famed. These pieces come from old style copper mines, no longer economically viable as such, but that have been operational for much of the past 2,500 years. Nowadays limited to the production of mineral specimens (and the price on such a piece is pretty eye watering) these mines have only recently become aware that their pieces display a beauty that the more common African material lacks. Extracting these intact is quite a challenge but their beauty is well worth it. Loz

Supergene oil palm seedlings in Nigeria have become very popular among oil palm farmers. Supergene oil palm seedling has hybrid characteristics compared to the Tenera and Nosefera varieties. What is Supergene Oil Palm Seedlings? Supergene oil Palm is a hybrid variety of oil palm species and a well-known oil palm in Malaysia. Supergene oil palm has a high growth rate and high production of palm…