A rock collection is a map of the Earth’s history in your hands. Each specimen tells how it formed:
from cooling magma, from layers of sediment, or from older rock changed by heat and pressure. What
turns a stone into a specimen is knowing where it came from.
Getting Started
ordicio follows the three classes geologists use:
Igneous rocks: plutonic rocks that cooled deep underground, such as
granite and gabbro, and volcanic rocks, such as basalt, rhyolite and obsidian.
Sedimentary rocks: clastic rocks made of fragments, such as sandstone
and conglomerate, and chemical or biogenic rocks, such as limestone and chert.
Metamorphic rocks: foliated rocks, such as slate, schist and gneiss,
and non-foliated rocks, such as marble and quartzite.
A classic start is a teaching set with one good example of each common rock type. Many collectors
then follow a region, a mountain range or the rocks along a geological boundary.
What to Record
Rock name and its class, as precisely as you can: “biotite granite” says more than “granite”.
Locality: outcrop, quarry or road cut with coordinates if possible, and the date you collected
it.
Geological unit and age: the formation or intrusion, and the period, from a geological map of
the area.
Texture and minerals: grain size, the main minerals you can see, fossils or structures.
Size and preparation: hand specimen, slab, polished face or thin section.
Care and Storage
Number each specimen with a small painted label and keep a matching card or record, so a specimen
and its data can always be matched again. Store specimens in trays or drawers so they do not rub
against each other. Respect collecting rules: many sites are protected, and quarries need
permission.
Mistakes to Avoid
Collecting loose stones from a beach or riverbed and recording them as the rock of that place -
they may have travelled far.
Skipping the date and exact place because “you will remember”.
The 30 fields worth recording for rocks, grouped as in the
ordicio app.
Identification
Rock name Text
Petrographic name, e.g. granite, basalt, sandstone, gneiss.
Texture Text
Grain size and fabric, e.g. coarse-grained, porphyritic, vesicular, foliated, cross-bedded.
Mineral content Text
Main minerals and their approximate shares.
Colour Text
Colour or colours as seen in daylight, main colour first.
Geology
Geological unit and age.
Formation Text
Rock unit (lithostratigraphy), e.g. Hell Creek Formation, Solnhofen Limestone, Posidonia Shale.
Geologic period Choice
Geologic period after the International Chronostratigraphic Chart (ICS 2024/12); Ma = million years ago.
13 choices
Precambrian (before 538.8 Ma)
Cambrian (538.8 to 486.9 Ma)
Ordovician (486.9 to 443.1 Ma)
Silurian (443.1 to 419.6 Ma)
Devonian (419.6 to 358.9 Ma)
Carboniferous (358.9 to 298.9 Ma)
Permian (298.9 to 251.9 Ma)
Triassic (251.9 to 201.4 Ma)
Jurassic (201.4 to 143.1 Ma)
Cretaceous (143.1 to 66.0 Ma)
Paleogene (66.0 to 23.0 Ma)
Neogene (23.0 to 2.58 Ma)
Quaternary (2.58 Ma to today)
Epoch / stage Text
Finer age, e.g. Late Cretaceous, Maastrichtian; Middle Devonian, Eifelian.
Age (Ma) Number
Age in million years, when known from the literature or a dating.
Specimen
Preparation Choice, or your own
How the sample is prepared.
Hand specimen (rough)
Cut slab
Polished
Thin section
Sphere / carving
Height (cm) Number
Height, measured upright as the object is meant to stand or hang.
Width (cm) Number
Width, measured from the front.
Depth (cm) Number
Depth, measured from front to back.
Weight (g) Number
Weight of the object (without stand, frame or holder unless noted).
Origin
Locality Text
Exact find site, as specific as possible, e.g. quarry, mine and level, beach, outcrop.
Region Text
State, province, county or district of the locality.
Country Text
Country of origin or issue, by its usual English name (historic states as named at the time, e.g. Kingdom of Bavaria).
Coordinates Place
Geographic position of the locality (keep private for sensitive sites).
Collected by Text
Person who collected or excavated the specimen.
Collection date Date
Date the specimen was collected in the field.
Acquisition
How and when the object came into the collection.
Acquisition date Date
Date the object came into the collection.
Acquisition method Choice, or your own
How the object came into the collection.
Purchase
Auction
Gift
Inheritance
Exchange / trade
Self-collected / found
Commission
Acquired from Text
Seller, auction house (with sale and lot number), donor or place where it was found.
Purchase price Amount
Price paid including fees and premiums.
Provenance Text
Earlier owners and the object's history, oldest first, with sources (labels, invoices, sale catalogues).
Value
Estimated and insured value.
Estimated value Amount
Current market value as estimated.
Valuation date Date
Date of the current value estimate.
Valuation basis Choice
What the estimated value is based on.
Own estimate
Recent sales / auction results
Dealer offer
Catalogue value
Professional appraisal
Insurance valuation
Insured value Amount
Sum the object is insured for.
Collection record
Your own inventory data.
Inventory number Text
Your own number or label for the object, e.g. C-0042, as written on its label or album page.
Storage location Text
Where the object is kept, e.g. room, cabinet, drawer, album and page, box.
Standards and References
The data sheets follow the standards collectors, dealers and museums use:
Nickel-Strunz classification, 10th edition (classes 1 to 10); IMA list of mineral species; mindat.org localities
AFMS and dealer usage for specimen size classes (thumbnail, miniature, small cabinet, cabinet)
IUGS classification of igneous rocks (QAPF), standard sedimentary/metamorphic classes
Meteoritical Society nomenclature, Meteoritical Bulletin Database; shock stages S1 to S6 (Stoeffler et al.), weathering grades W0 to W6 (Wlotzka)
GIA diamond grading (colour D to Z, clarity FL to I3, cut); CIBJO / LMHC nomenclature for gem treatments; pearl value factors
Updated October 24, 2026
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