Carnelian, and the reason a red stone sits at the head of this list goes back to a decision about where a circle should start. Bloodstone, red jasper, garnet, aquamarine and diamond make up the rest of it.
A circle has no beginning. One has to be chosen, and the zodiac Western astrology uses is pinned to an astronomical instant: the moment the Sun crosses the celestial equator moving north, at the spring equinox. The first thirty degrees after that instant are Aries.
It was not always laid out that way. The uniform twelve-part zodiac is a Babylonian construction, introduced between 409 and 398 BCE and probably within a very few years of 401, and it was measured against the fixed stars. Hipparchus is who re-anchored it, later, in the Greek-speaking world. Ptolemy comes next, named by the Internet Encyclopedia of Philosophy as the first astrologer to employ Hipparchus’s zodiac modified to account for the drift of the equinox against those stars, and that encyclopedia describes what the modified version does in one line: it “uses the vernal equinox as the beginning point rather than the beginning of one of the twelve constellations”. Western practice has used it ever since.
Aries is therefore first by construction. What crystal practice credits the sign with, the initiative and the appetite for starting a thing, sits on top of a position in a coordinate system, and the stones were chosen to suit the character afterwards.
Where the circle was decided to begin
Two things follow from the anchoring, and both are visible in the stone lists. The first is that the signs and the constellations they are named after came apart. The equinox moves against the background stars, slowly and continuously, so a zodiac tied to the equinox drifts away from a zodiac tied to the stars. Aries the sign and Aries the constellation have not sat on top of one another for a long time, which is a fact about two measuring conventions and not an error in either. Nobody using the tropical zodiac has ever claimed to be pointing at the stars. The Libra list meets the same thing from the opposite side of the circle, where the September equinox is the boundary and the boundary moves by hours from year to year.
It also means the sign begins at an instant and not on a date. The US Naval Observatory puts the 2026 March equinox at 14:46 UT on 20 March, and the instant slides by several hours from one year to the next, so the first day of Aries is a calculation rather than a fixture in the calendar. Almanacs print 21 March because a printed table needs a day in it.
The second thing that follows is that a year anchored at the spring equinox and a circle anchored at the spring equinox start together. A table of twelve signs and a table of twelve months therefore line up, and a compiler who has both in front of him can label one series twice. The oldest surviving sign list does exactly that, which is where the modern confusion between a sign stone and a month stone begins.
Sardonyx, and the column it sits in
Cornelius Agrippa printed his table of correspondences in 1533, in the “Scale of the Number twelve” in Book II of the Three Books of Occult Philosophy. Three rows sit directly above one another: the twelve signs of the zodiac, the twelve months beginning with March, and twelve stones. Sardonyx sits under Aries and under March at once, because in that table Aries and March are one column.
The other lists disagree with him and with each other. Aries gets crystal from a Spanish treatise of 1604, printed at Valladolid by Morales, which George Frederick Kunz reproduces and cites to folios 15a and 15b. Kunz’s own list of 1913 gives bloodstone and gives no source for it. The shops give carnelian.
Four answers, and carnelian appears in none of the three older ones. Agrippa does list carnelian. He puts it under Taurus. Nothing was handed down here: four compilers wrote four lists in four centuries, none of them working from an earlier one, and ours is a fifth.
The stones, and what most of them are
The Aries list is red first and specific second, and the redness is doing more work than the mineralogy. Carnelian, bloodstone and red jasper are all chalcedony, which is quartz grown at a grain size too small to resolve by eye. Not one of them is a mineral species and not one has an entry of its own in the Handbook of Mineralogy. All three sit at Mohs 7 and behave identically in the hand. What separates them is appearance. Carnelian is translucent and orange-red; bloodstone is dark green, carrying red iron oxide flecks; red jasper is opaque and even in colour.
Because the three names cover one material, nothing about a given piece decides which of them it is sold under except its colour. Colour is also the property most easily supplied. GIA’s treatments page names chalcedony and quartz in a list of materials dyed “since ancient times”, alongside coral, turquoise, lapis lazuli and howlite. A red jasper tumble whose colour is too uniform to be plausible is not a rare thing on a market stall.
Garnet is a group. Almandine and pyrope, both at Mohs 7 to 7.5, are what lies behind most of the red material sold under the name, and neither word reaches a shop label. A garnet tumble and a carnelian tumble are two different minerals doing one job on this list, and the job is the colour. Nothing on the Aries list was picked for hardness, formation or locality, and it shows. Four of the six are red or carry red through them, one is blue and one is colourless.
Aquamarine and diamond arrive by calendar. Aries runs from about 21 March to about 19 April, so it collects March and April, and aquamarine is March’s stone while diamond is April’s in the list Jewelers of America maintains. Kunz, writing the year after, records that list as approved at a meeting in Kansas City in August 1912. Jewelers of America names the body as the American National Retail Jewelers Association and itself as its successor. Aquamarine is beryl with a blue colour, Mohs 7.5 to 8. Diamond has a Handbook page under its own name: carbon, cubic, Mohs 10, perfect cleavage on the octahedral planes, and the highest thermal conductivity of any known substance.
Look any of these up by the name on the label in the Crystalance Mineral Library and the entry you reach is quartz.
None of which touches what the list is built on. Somebody had to decide where a circle begins. The decision landed on an astronomical instant in spring, the sign holding the first thirty degrees after it became the sign of starting things, and the stones were picked afterwards to suit that. If carnelian was attached to Aries before 1900 the attribution has not turned up, and the stone at the head of the list has changed at least three times in four centuries. The position it is attached to is zero degrees of celestial longitude, measured from the spring equinox, and that has not moved since Ptolemy.
Sources
- Britton, J.P., “Studies in Babylonian lunar theory: part III. The introduction of the uniform zodiac”, Archive for History of Exact Sciences 64 (2010), 617 to 663: link.springer.com
- Internet Encyclopedia of Philosophy, Hellenistic astrology, on Hipparchus, Ptolemy and the tropical zodiac: iep.utm.edu
- Cornelius Agrippa, Three Books of Occult Philosophy, Book II ch. XIV, in the 1651 English translation of the 1533 original: archive.org
- George Frederick Kunz, The Curious Lore of Precious Stones, 1913, ch. X: gutenberg.org
- US Naval Observatory, seasons and equinox times: aa.usno.navy.mil
- Jewelers of America, birthstone list and its history: jewelers.org
- GIA, gem treatments, on dyeing: gia.edu
