Not yet confirmedUnder investigation. Here is what is known and what still needs proof.
In one corner of the Tel Shiqmona mound, a space about two meters by two on Israel’s Carmel coast in Haifa, sat a stone for crushing olives and a floor thick with animal dung. In the room next door lay a heap of crushed murex shells, the sea snail that gave kings and priests their blue and purple dye.
What looks like a mess is, according to a peer-reviewed study published September 24, 2026, in PLOS One, the signature of an industrial compound that changed jobs through the year. The University of Haifa team proposes that the switching followed the seasons. That second part is a model, not something read directly from the soil.
The sediments show the same space was used, at different times, for olive oil, weaving, sheltering livestock and dye.
The site covers about two acres on the southern edge of Haifa and, the authors say, is the largest known Iron Age purple-dye factory in the Mediterranean. The level studied, Stratum 11, spans roughly 790 to 740 B.C., the time of Jeroboam II in the Kingdom of Israel, the northern kingdom.
Pottery jugs from Tel Shiqmona at the National Maritime Museum in Haifa: right, a Cypro-Phoenician jug of the 10th century B.C.; left, a Phoenician jug of the 8th century B.C. Photo: Hanay, CC BY-SA 3.0, Wikimedia Commons
Dung, ash and shells: what the microscope read in two tiny spaces
The 2023 dig, directed by Golan Shalvi, took place in a section that threatened to collapse during conservation work by the Israel Nature and Parks Authority. It yielded 28 loose sediment samples and three undisturbed blocks, analyzed with infrared spectroscopy (FTIR), micromorphology and counts of microscopic plant, ash and dung remains. Isaac Ogloblin Ramírez and Madeline Jacobson handled the lab analysis. The article’s editor at the journal was Joe Uziel of the Israel Antiquities Authority.
In the eastern space, two meters by two, the layer sitting on the packed-earth floor held up to 2.53 million dung spherulites per gram of sediment, and the next layer reached 4.48 million. The reference soil beneath the floor held 0.57 million. These spherulites form in manure and survive for millennia. Organic fragments broken in place point to trampling: animals were kept there.
The thin laminae, one to three millimeters thick, alternate brown dung with gray wood ash. The authors read the ash as sanitation: alkaline, it neutralizes odors and controls pests, and was likely spread before the space went back to work. There are also signs of fire on the floor itself, a reddened layer with charcoal and ash on top.
In the neighboring space, about 3.5 by 2 meters, were the pile of murex shells, dozens of uncharred olive pits and an olive-press weight bearing olive impressions. Nearby, from earlier excavations, came dyeing-vat fragments with vivid purple stains. The fire residues, the authors suggest, come from heating water to add to the vats, since the vats themselves show no sign of direct fire.
The calendar is an inference: what the study proves and what it proposes
The authors themselves separate two things. Multifunctionality, the use of one space for different, non-simultaneous activities, is documented by the finds. Seasonality, the order of those activities across the year, is an inference from when each was known to happen. The deposits themselves do not show the season; the calendar comes from outside them.
Olive harvesting and pressing run from October to December. Textile work follows the spring shearing. Sheltering animals would fill the idle months, probably winter. Based on the known timing of the activities, the researchers built a model: olive pressing in autumn, animals in winter, textile work in spring.
And the dye? The paper’s abstract says purple production was probably woven into the cycle, in complementary windows. Its precise season cannot yet be established. Summaries that cast olive oil, cloth and livestock as what happened in the months without dye go beyond the paper: the dye season is the gap in the model.
The only ancient support comes from Pliny the Elder, who writes in Natural History IX, 62 that the best time to take these shellfish is after the rising of the Dog Star, or before spring, that is, late summer to late winter. The study notes that Pliny’s testimony is debated. A practical reason remains: thousands of mollusks are needed for a single vat, and year-round harvesting would deplete local populations. Rough seas and dye quality would also matter.
Then there is sample size. The analyses come from two small spaces. That the whole compound ran on a synchronized rotation is, the authors write, an extrapolation beyond the sampled contexts. They offer it as the most economical reading and note that cleaning and re-laid floors between cycles would have erased the fine layers of each season.
The purple factory the northern kingdom took from the Phoenicians
Tel Shiqmona was excavated by Joseph Elgavish in the 1960s and 1970s, by Shay Bar from 2011 to 2013 and by Shalvi in 2023. Elgavish’s finds, recovered between 1963 and 1977 for the Haifa Museum, sat in storerooms for half a century. In 2025, Shalvi told ZME Science it would be an exaggeration to call the place “a very purple place”; making the dye, he noted, was not glamorous.
In April 2025 the same team published in PLOS One the study that identified the site, with 176 artifacts tied to purple-dye production, 135 of them stained, according to the Times of Israel. Industrial-scale production existed by the 9th century B.C., not only in Roman times, Ayelet Gilboa said. “It was not just one individual dyeing a garment for a king,” she said.
According to Shalvi, the place began as a small Phoenician village that already dyed, though not at industrial scale. In the 9th century B.C. it stopped being residential, gained a fortification wall and became an industrial hub, and inland motifs appear, meaning Israelite ones. After the Assyrians toppled the Kingdom of Israel, production dipped briefly and then resumed on a large scale, probably under Phoenician management, perhaps from Tyre.
Stratum 11 was the peak. It yielded more than 40 dye-related artifacts, over half of them stained, and at least 16 dyeing vats of about 350 liters each, not necessarily in use at once, plus at least two olive presses. In Building B283, well preserved, an olive press, a stained vat and 16 loom weights turned up in place, the remains of one or two looms. The occupation ended in violent destruction. Afterward, Stratum 10 returned the site to livestock, with a four-room house serving as a farmstead.
Blue and purple in the Bible, from the Tabernacle to the Temple
The Bible names the dye the site produced. In Exodus 25:4, the offerings for the sanctuary include blue (techelet), purple (argaman) and scarlet yarns. Numbers 15:38 commands a blue cord on the tassels of garments. In 2 Chronicles 2:7, Solomon asks the king of Tyre for a craftsman skilled in purple, crimson and blue, and 2 Chronicles 3:14 describes the Temple veil in those colors. Ezekiel 27:7 lists the blue and purple from the coasts of Elishah among Tyre’s luxuries.
Who supplied the Jerusalem Temple is a matter of hypothesis. In 2025, Shalvi told the Times of Israel that Tel Shiqmona is, in his view, the strongest candidate for supplying the First Temple, and that the Israelites likely exported the dye to Philistia, Moab, Edom and Judah. The Temple link is the researcher’s opinion, not a result of the 2026 study, which concerns seasonal use of space. Gilboa added that Assyrian documents, such as Sennacherib’s Cylinder of about 690 B.C., mention techelet and argaman, and that there is now proof of mass production at the time.
Stratum 11 coincides with the reign of Jeroboam II and the time of the prophet Amos. According to 2 Kings 14:23-29, Jeroboam reigned in Samaria for 41 years; Amos 1:1 places the prophet in that period. Amos 6:4-6 speaks of those who lie on beds of ivory and anoint themselves with the finest oils. The study does not discuss these texts, but its bibliography includes a 2026 article by Omer Sergi and J. J. Krause on social criticism in Amos in light of recent archaeology. Pressed olive oil also appears in the Law: the beaten oil for the Tabernacle lamp (Exodus 27:20).
Centuries later, purple remains in the New Testament. Lydia of Thyatira sold purple goods and hosted Paul in Philippi (Acts 16:14-15). Soldiers dressed Jesus in a purple robe (Mark 15:17).
What the authors argue and what comes next
For Shalvi, the lesson is about method. “When archaeologists find an olive press, the natural tendency is to say, ‘Olive oil was produced here,’” he said in the university’s press release, noting that the harvest lasts only a short time in late autumn. The question the study leaves for any site is what happened there in the months when the industry stood idle.
David Friesem, head of the university’s Laboratory for Environmental Micro-History, says the seasonal pattern at Shiqmona could be found at other sites through integrated research, and that making the most of resources and space was a feature of ancient societies “no less than of our own.” The authors see the flexibility as a logistical necessity on a site of about two acres, and also a sign of sophisticated management of the kingdom’s assets. Green Prophet, reading the study through an architect’s lens, sees in it a model of flexible building use.
What is missing is a way to measure the season in the material itself. The paper says stable-isotope analysis, or growth-line analysis of the murex shells and faunal remains, could test the calendar directly. The authors say they plan a dedicated study to work out in which season the purple dye was made.
