Collectors may find it confusing to understand the many slight distinctions that separate different varieties of Quartz.
As the last stage of the BRS, on the Felsic or sometimes now called the Sialic end of both the continuous and discontinuous series, Quartz crystals form at lower temperatures than other igneous rock, and in more “depleted” magma chambers, after other minerals have precipitated out of the magma mixture.
This leaves white to clear silica, the primary component of quartz, as the “leftover material” after most of the calcium, magnesium, and potassium rich minerals have formed. So what's left at this point, is a lot of silica and some iron and other elements. Thus the classic term Felsic (Fe for iron) and (Si for Silica).
So this can partly explain why mountains tend to be made of granite, which is the plutonic rock formed underground at this point in the Bowen Reaction Series, then slowly uplifted and brought to the surface as overlapping materials weather away. So from this description, it is fair to assume that quartz is quite abundant! It must be, since it forms of these common components, and mountains, indeed entire mountain ranges may be primarily composed of quartz-rich rock.
So as a collector you might think quartz is boring- as it is clearly not especially rare. But you might be surprised to learn that it is in fact one of the most diverse minerals, forming in hundreds of different varieties and forms, containing many different inclusions of all colors, various coatings, and may form crystals of many types, shapes, sizes and colors.
In this list, we will outline some of the amazing types of quartz, what distinguishes them and how to tell them apart.
First it's important to understand the difference between an element a mineral and a rock, so if you are unclear on this please read the about section first.
Understanding that elements form minerals, and minerals form rocks, We must also note that in mineral collecting there are both formally recognized mineral groups and mineral varieties, and informally recognized mineral trade names. There are also formal and informal trade names for some rocks! Since quartz can really be any of these, we have tried to differentiate between these groups for collectors.
So even though terms like Amethyst, Citrine, and Rose Quartz are widely recognized by most enthusiasts, In the world of mineralogy, these names do not mean anything. They are all simply the mineral quartz, with some inclusions of iron in different concentrations, lending them these various hues of purple, orange and pink.
Popular trade names for Quartz Crystals:
- Amethyst - purple to blue quartz
- Citrine - red orange to yellow quartz. Citrine may be artificially produced by hearing amethyst, so an experienced dealer can usually tell the difference between natural citrine and the intensely orange brown hue of heated amethyst
- Rose Quartz - pink quartz, which is a lighter version of amethyst, and not commonly found in well crystallized formations.
- Chlorite Quartz - forest green to dark green quartz that may appear as a coating or inclusion
- Prase Quartz - a macrocrystalline coated quartz with green inclusions or exclusiontypically consiting of actinolite (*or possibly hedenbergite).
- Lithium Quartz- frequently appears as a light to medium blue hue that may be slightly more intense towards the attachment point, but generally it just creates a steely blue tint to the entire crystal
- Dumortierite included Quartz - a popular form of quartz that forms with distinctive sprays of intense, dodger blue dumortierite at the base of the crystals
- Tourmalated Quartz- containing tourmaline inclusions, frequently black schorl or dark brown Dravite, but may in extraordinary samples contain colorful tourmaline like blue indicolite.
- Rutilated Quartz- containing usually gold colored rutile inclusions.. The best samples have very clear quartz with well defined shafts or v-twins of rutile
- Sunshine or Corona Quartz- bright yellow with intense halloysite inclusion or coating, also called mango quartz
- Hematoid Quartz - usually a red to brown hematite / iron coating on quartz
- Spirit Cactus or Cactus Quartz - usually clear to purplish drusy coating of small quartz crystals under 1 mm on a larger quartz crystal, resembling the spikes of a cactus like a saguaro
Locality specific trade names:
- Herkimer Diamonds - Very clear to slightly smoky colored quartz, often found as doubly terminatd floater crystals or in hllow vugs in a groundmass, up to 5 cm or greater in size.
- Lake County Diamonds - Tiny less than 2 cm eye clear quartz floaters found near the base of Mt. Konocti, Lake County, California.
- Pecos Diamonds - Small well terminated floaters, which may be cloudy or coated with hematite, occurring in the area near Pecos New Mexico.
- Payson DIamonds - Clear to cloudy skeletal quartz found near Diamond Point in Payson, Arizona.
Trade names for Quartz rich silicate rocks:
- Chalcedony - a translucent microcrystalline quartz rock
- Agate - banded or layered microcrystalline quartz with some translucency in distinct bands
- Jasper - an opaque microcrystalline quartz rich rock
- Opal - a mineraloid of hydrous, non crystalline silica
Interesting growth patterns
- Faden - a form of quartz that displays a white line between points on opposite sides, caused by microscopic fractures and recrystallization in two opposing directions along the same plane
- Gwindel - a form of quartz in which a single crystal curves along the c-axis forming a distinctive twist effect
- Needle - this term describes quartz that are particularly long relative to their width, appearing like long six sided needles with sharp points
- Fenster- a fenster quartz is characterized by a quartz crystal, which is frequently a doubly terminated floater crystal, that has many distinct skeletal shapes, windows and chambers, and often has inclusions of clay or hematite, creating especially visually complex and pleasing crystal formations.