# Lithology

> The lithology block of a .well file: a list of Lithology objects.

Property `lithology` of the .well root, an array of objects, required. [Defined in the spec](/format/spec/v2/object-schemas#lithology--lithology).

| Field | Type | Required | Values / constraints | Description |
| --- | --- | --- | --- | --- |
| `from` | number | yes |  |  |
| `to` | number | yes |  |  |
| `description` | string | yes |  |  |
| `color` | string | yes |  |  |
| `texture` | object | yes |  |  |
| `texture.code` | string \| number | yes |  |  |
| `texture.vocabulary` | string | no |  |  |
| `geologic_unit` | string | yes |  |  |
| `aquifer_unit` | string | yes |  |  |