Vanadinite belongs to the apatite group 0f phosphates, and has the formula of Pb5(VO4)3Cl. It is formed by the oxidation of lead ore deposits, and by weight its content is almost 75% lead. The specimen is from Morocco, and is composed of the typical flattened hexagonal red crystals.
Rutile TiO2 is titanium oxide. The occurrence of rutile crystals enclosed in quartz is not uncommon. It is thought that hydrothermal fluids carrying quartz and other minerals invade a cavity, and on cooling, mineral crystals are first deposited, and on further cooling quartz is deposited, enveloping and preserving the previously deposited crystals. In this specimen there are many acicular crystals of a yellow/golden colour. Rutilated quartz has earned the nickname of "Maidens hair quartz". The locality of the specimen is only known as New Zealand.
Rhodochrosite is Manganese carbonate MnCO3. This specimen is the product of brecciation, a mixture of rhodochrosite, and an unknown white mineral. I was puzzled by the very dark colour of the rhodochrosite which would normally be a shade of pink, but discovered in Macdonalds book that when exposed to air rhodochrosite becomes covered with a thin film of manganese through oxidation. The unknown white mineral is zeolitic in appearance, though unlikely, note inset picture of a spray which is about 3mm. One surface of the specimen is coated with numerous pyrite cubes average 1,5 mm.
Another example of calcite crystals, again from one of the limestone quarries of South Wales. Calcite is Calcium carbonate CaCO3, and these crystals are of the variety known as "nailhead". The colour is cream with a hint of orange, and no other minerals present. I collected this specimen many years ago from Ton Mawr quarry, in South Wales.
Gypsum, CaSO4 . 2H2O Calcium sulphate dihydrate, is an evaporite mineral, which is deposited when salt lakes and playas dry up. This specimen has a fibrous habit, and is commonly referred to as satin spar. It is a very ordinary specimen, but commands a special place in my collection, because it was given to me by Gwyn Billington of the Russell Society many years ago, when I first started collecting minerals. Sadly Gwyn died many years ago, but I vividly remember sitting in his cluttered living room on many occasions. The label describes the location, Penarth beach, South Wales.