#lead minerals

[mymineralbox]

Pyromorphite: Lead’s Bright Green Signature

Pyromorphite — Pb₅(PO₄)₃Cl — is lead’s contribution to the mineral world’s green palette. A lead chlorophosphate, it forms in the oxidation zones of lead ore deposits, where primary lead sulfides (galena) slowly break down in the presence of phosphate-rich groundwater.

The vibrant lime-green color comes from trace impurities and the crystal structure itself. Pyromorphite crystallizes in the hexagonal system, producing classic barrel-shaped prismatic crystals with crisp hexagonal cross-sections.

Key facts:

• Chemistry: Lead chlorophosphate — Pb₅(PO₄)₃Cl

• Mohs hardness: 3.5–4

• Specific gravity: ~7.0 — heavy; you feel the lead in the hand

• Crystal system: Hexagonal

• Color: Bright green, yellow-green, sometimes brown or orange

• Type locality: Zschopau, Saxony, Germany (1813)

Guangxi Province in China is one of today’s top sources for top-shelf pyromorphite specimens — the Chinese material is known for its saturated lime-green color and well-formed barrel crystals on quartz matrix.

[mymineralbox]

— Morocco. Vanadinite is lead vanadate chloride (Pb5(VO4)3Cl), and it's a secondary mineral that forms in the oxidized zones of lead ore deposits where vanadium-bearing fluids react with weathered galena. The Mibladen and ACF districts in Morocco have produced the world's best-known vanadinite specimens for about a century, and the signature orange-red color comes straight from the vanadium itself. Collector notes: vanadinite is heavy (specific gravity 6.8–7.1 — you can feel the weight the moment you pick it up) and soft (Mohs 3), so it needs gentle handling. Under a hand lens, you can sometimes see the classic hexagonal hollow-ended prismatic crystals that make it unmistakable.

[mineralogue-blog]

Bayldonite is a relatively rare green secondary arsenate mineral. It has the chemical composition PbCu3(AsO4)2(OH)2 and occurs in oxidised zones of copper- and lead-bearing deposits. It occurs in various shades of green, and has an apple-green streak.

Sources:

Mindat

Webmineral

Image 1:  Bayldonite pseudomorph after mimetite from Tsumeb, Namibia. (c) Rob Lavinsky and irocks.com  Image 2: Acicular bayldonite in bayldonite vug from Tsumeb, Namibia. (c) Rob Lavinsky and irocks.com

[mineralogue-blog]

Boleite is a deep blue halide mineral with the chemical formula KPb26Ag9Cu24(OH)48Cl62. It occurs in the oxidized zone of Pb-Cu deposits where chloride solutions have reacted with primary sulphides. It is named after its type locality: Boleo, Baja California, Mexico.

It is transparent and deep Prussian blue to indigo in colour, with a greenish blue or light green streak and a Mohs hardness of 3-3.5. Crystals usually appear as cubes, but are in fact rectangular crystals twinned in such a way that they appear cubic.

Sources:

Mindat

Webmineral

Wikipedia

Image sources: 1, 2, 3

[mineralogue-blog]

Galena is the naturally occurring mineral form of lead (II) sulphide, with the chemical formula PbS. It has been known since at least 3000BC as a lead ore, and it remains the main lead ore to this day. It was named by Pliny the Elder from the Greek galene, meaning lead ore.

Galena is a soft, heavy lead-grey mineral, with a hardness of 2.5—about the same hardness as a fingernail—and a specific gravity of 7.2-7.6. Specific gravity is a measure of density, calculated with the formula d = (weight in air) ÷ (weight in air – weight in water). Samples of galena feel significantly heavier than other mineral samples of similar size. It has a lead-grey to greyish-black streak and a metallic lustre, although it gains a dull tarnish when exposed to air.

Galena has an isometric crystal system, and crystals may be cubes or, octahedrons, or a combination of the two. It displays perfect cleavage.

Silver very frequently occurs as an impurity in galena deposits, to the extent that galena is an important silver ore. Copper, iron, and bismuth are other common impurities. Galena frequently occurs with other metal sulphides, including sphalerite, pyrite, and chalcopyrite.

Sources & further reading:

Webmineral and their page explaining specific gravity

Mindat 

University of Minnesota

Minerals.net

Wikipedia

Images sources: 1 (Galena with barite and pyrite ), 2