#ludlamite

Ludlamite

Here we have a rare phosphorous rich mineral that forms in hot fluid rich environments such as the last cooling remnants of granites (called pegmatites) or rocks that have been altered by the ubiquitous hydrothermal fluids of the Earth. These can take many forms, from fluids spat out of lavas to basinal brines expelled as rocks are compressed by the younger rocks above. All of these carry their dissolved components, and frequently mobilise elements from vast volumes of rock to concentrate them elsewhere, forming most of our ore deposits.

This one segregates some of the 'denser' elements, those more common in the Earth's mantle like iron and magnesium. It was first discovered in the pegmatites of the Wheal Jane mine in Cornwall when it was reopened after a period of fallowness. These granites of south west England were a well known source of tin and other metals for thousands of years, and legends say that Jesus may have accompanied Joseph of Arimathea on a tin buying trip there (said legend being the basis of the poem by William Blake later adapted into the well known hymn Jerusalem).

The mineral was named after an English mineralogist in 1877. Ludlamite is a often a secondary mineral made from remobilised phosphorous though it also occurs in the complex polymetallic veins that spat out of those long ago magmas of the Cornish batholith before they froze. Colour is usually green, though colourless and bluey material also exists, iooften as sprays of sheaves. It is too soft (a mere 3.5 on Mohs scale) for faceting.

The original mine has been reopened again, this time uniquely for Ludlamite rather than the ores that were once thought important... with only a few known localities on the planet such a mineral rarity is worth the effort. Other places include La union in Spain, Rapid Creek in the Yukon and a few places in the USA. This 4.5 x 2.7 x 1.6 cm specimen was mined in Brazil.

Loz

Image credit: Rob Lavinsky/iRocks.com

Ludlamite, Siderite

Ludlamite