Pyrite, Quartz & Sphalerite
Pyrite is a common iron sulphide mineral found in many different geological settings. It has a brassy-yellow metallic colour that has caused many people to mistake it for gold, giving it the name “Fool’s gold”. Pyrite and gold can be quite easily distinguished from one another: pyrite is less yellow and much lighter and harder than gold, which can be scratched with a pocket knife. Pyrite often forms perfect cubes, which can grow to quite large sizes, because of its crystal structure. The word pyrite comes from the Greek word ‘pyr’ meaning fire, because it will spark if hit with other metal or stone objects.
Quartz is the second most abundant mineral on Earth, present in many different types of rocks. Although usually clear or milky white in colour, quartz is found in a variety of colours due to impurities in the crystal structure. Pure quartz consists of silicon and oxygen only, but atoms of other elements often make their way into the quartz crystal structure, colouring the crystals. Some varieties of quartz, like purple amethyst and yellow citrine, are considered to be semi-precious gemstones and have been used since ancient times to make jewellery and decorative objects. Well-formed (euhedral) crystals of quartz have a hexagonal cross section and are highly collectible.
Sphalerite is the main ore mineral for zinc, and although relatively common, finding it in commercial amounts is somewhat rarer. The zinc will give the mineral a yellow or red hue, but iron can replace the zinc in the atomic structure, making the crystals black. Rarely, cobalt finds its way into the structure, and produces green crystals. Although sphalerite is a relatively soft mineral, it can be cut (faceted) into attractive gems, which are used for mineral displays.
This sample is from the American Creek area near Stewart in northwestern BC.
Several mineral occurrences are documented in the area. Most are polymetallic veins less than a metre wide that are related to faulting. Polymetallic veins are veins that contain several different types of metallic ore minerals. In the American Creek area, the main ore minerals are pyrite and sphalerite, as seen in this sample, as well as galena (lead sulphide), chalcopyrite (copper sulphide) and, less commonly, silver and gold. The veins are mostly filled with quartz and calcite, two common gangue (waste) minerals.
Small prospects were staked in the 1900s-1930s but little mining or exploration work has taken place along American Creek since.
Store: Association for Mineral Exploration (AME)
Accession #: AME 961
Primary Mineral: Pyrite, Quartz & Sphalerite
Secondary Mineral: –
Site Locality: American Creek
Location: Stewart, British Columbia
Special Features: n/a